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Aguirre NM, Ochoa ME, Holmlund HI, Palmeri GN, Lancaster ER, Gilderman GS, Taylor SR, Sauer KE, Borges AJ, Lamb AND, Jacques SB, Ewers FW, Davis SD. How megadrought causes extensive mortality in a deep-rooted shrub species normally resistant to drought-induced dieback: The role of a biotic mortality agent. PLANT, CELL & ENVIRONMENT 2024; 47:1053-1069. [PMID: 38017668 DOI: 10.1111/pce.14768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 10/21/2023] [Accepted: 11/03/2023] [Indexed: 11/30/2023]
Abstract
Southern California experienced unprecedented megadrought between 2012 and 2018. During this time, Malosma laurina, a chaparral species normally resilient to single-year intense drought, developed extensive mortality exceeding 60% throughout low-elevation coastal populations of the Santa Monica Mountains. We assessed the physiological mechanisms by which the advent of megadrought predisposed M. laurina to extensive shoot dieback and whole-plant death. We found that hydraulic conductance of stem xylem (Ks, native ) was reduced seven to 11-fold in dieback adult and resprout branches, respectively. Staining of stem xylem vessels revealed that dieback plants experienced 68% solid-blockage, explaining the reduction in water transport. Following Koch's postulates, persistent isolation of a microorganism in stem xylem of dieback plants but not healthy controls indicated that the causative agent of xylem blockage was an opportunistic endophytic fungus, Botryosphaeria dothidea. We inoculated healthy M. laurina saplings with fungal isolates and compared hyphal elongation rates under well-watered, water-deficit, and carbon-deficit treatments. Relative to controls, we found that both water deficit and carbon-deficit increased hyphal extension rates and the incidence of shoot dieback.
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Affiliation(s)
- Natalie M Aguirre
- Ecology and Evolutionary Biology Program, Texas A&M University, College Station, Texas, USA
- Natural Science Division, Pepperdine University, Malibu, California, USA
| | - Marissa E Ochoa
- Natural Science Division, Pepperdine University, Malibu, California, USA
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California, USA
| | - Helen I Holmlund
- Natural Science Division, Pepperdine University, Malibu, California, USA
| | | | - Emily R Lancaster
- Natural Science Division, Pepperdine University, Malibu, California, USA
- School of Marine Sciences, University of Maine, Orono, Maine, USA
| | - Gina S Gilderman
- Natural Science Division, Pepperdine University, Malibu, California, USA
| | - Shaquetta R Taylor
- Natural Science Division, Pepperdine University, Malibu, California, USA
| | - Kaitlyn E Sauer
- Natural Science Division, Pepperdine University, Malibu, California, USA
| | - Adriana J Borges
- Natural Science Division, Pepperdine University, Malibu, California, USA
| | - Avery N D Lamb
- Natural Science Division, Pepperdine University, Malibu, California, USA
- Nicholas School of the Environment, The Divinity School, Duke University, Durham, North Carolina, USA
| | - Sarah B Jacques
- Natural Science Division, Pepperdine University, Malibu, California, USA
- Department of Surgery, Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA
| | - Frank W Ewers
- Department of Biological Sciences, California State Polytechnic University, Pomona, California, USA
| | - Stephen D Davis
- Natural Science Division, Pepperdine University, Malibu, California, USA
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2
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Gričar J, Jevšenak J, Giagli K, Eler K, Tsalagkas D, Gryc V, Vavrčík H, Čufar K, Prislan P. Temporal and spatial variability of phloem structure in Picea abies and Fagus sylvatica and its link to climate. PLANT, CELL & ENVIRONMENT 2024; 47:1285-1299. [PMID: 38213092 DOI: 10.1111/pce.14811] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 12/05/2023] [Accepted: 12/30/2023] [Indexed: 01/13/2024]
Abstract
Using a unique 8-year data set (2010-2017) of phloem data, we studied the effect of temperature and precipitation on the phloem anatomy (conduit area, widths of ring, early and late phloem) and xylem-ring width in two coexisting temperate tree species, Picea abies and Fagus sylvatica, from three contrasting European temperate forest sites. Histometric analyses were performed on microcores taken from tree stems in autumn. We found high interannual variability and sensitivity of phloem anatomy and xylem-ring widths to precipitation and temperature; however, the responses were species- and site-specific. The contrasting response of xylem and phloem-ring widths of the same tree species to weather conditions was found at the two Slovenian sites generally well supplied with precipitation, while at the driest Czech site, the influence of weather factors on xylem and phloem ring widths was synchronised. Since widths of mean annual xylem and phloem increments were narrowest at the Czech site, this site is suggested to be most restrictive for the radial growth of both species. By influencing the seasonal patterns of xylem and phloem development, water availability appears to be the most important determinant of tissue- and species-specific responses to local weather conditions.
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Affiliation(s)
| | - Jernej Jevšenak
- Slovenian Forestry Institute, Ljubljana, Slovenia
- TUM School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Kyriaki Giagli
- Department of Wood Science and Technology, Faculty of Forestry and Wood Technology, Mendel University in Brno, Brno, Czech Republic
| | - Klemen Eler
- Department of Agronomy, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Dimitrios Tsalagkas
- Department of Wood Science and Technology, Faculty of Forestry and Wood Technology, Mendel University in Brno, Brno, Czech Republic
| | - Vladimír Gryc
- Department of Wood Science and Technology, Faculty of Forestry and Wood Technology, Mendel University in Brno, Brno, Czech Republic
| | - Hanuš Vavrčík
- Department of Wood Science and Technology, Faculty of Forestry and Wood Technology, Mendel University in Brno, Brno, Czech Republic
| | - Katarina Čufar
- Department of Wood Science and Technology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
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3
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Xu Z, Ran X, Zhang Z, Zhong M, Wang D, Li P, Fan Z. Designing a solar interfacial evaporator based on tree structures for great coordination of water transport and salt rejection. MATERIALS HORIZONS 2023; 10:1737-1744. [PMID: 36799081 DOI: 10.1039/d2mh01447e] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Solar interfacial evaporation has been receiving increasing attention but it is still a huge challenge to achieve excellent coordination between efficient water transport and salt rejection. Here, unlike the common wood-inspired evaporators with equal-diameter directional pores, we have constructed an integrated structure with highly connected gradient pores that mimic the xylem vessels and phloem sieve tubes found in trees. The bio-inspired structure can reduce the resistance of water transport and salt rejection in the same channel. The average transport speed of the 6.5 cm high (2 cm in diameter) porous structure reached 1.504 g s-1, and water was transported 16 cm after 100 seconds. Using multilayer graphene oxide as the photothermal conversion material, the evaporators with different heights can work for more than 9 hours under the condition of 1 sun illumination and 23 wt% brine without any salt crystallization, and the evaporation rates range from 3.28 to 4.51 kg m-2 h-1, with the highest energy utilization efficiency of about 80%. When used in heavy metal treatment, the rejection was greater than 99.99%. This research provides a simple but innovative design idea for evaporators and is expected to further expand the application of solar interfacial evaporation.
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Affiliation(s)
- Zhicheng Xu
- School of Materials Science and Engineering, South China University of Technology, Guangzhou, 510640, China.
| | - Xueqin Ran
- School of Materials Science and Engineering, South China University of Technology, Guangzhou, 510640, China.
| | - Zhijie Zhang
- School of Materials Science and Engineering, South China University of Technology, Guangzhou, 510640, China.
| | - Mingfeng Zhong
- School of Materials Science and Engineering, South China University of Technology, Guangzhou, 510640, China.
| | - Da Wang
- School of Physics and Optoelectronics, South China University of Technology, Guangzhou, 510640, China
| | - Pengping Li
- Key Laboratory of Harbor and Marine Structure Durability Technology Ministry of Communications, Guangzhou, 510230, China
| | - Zhihong Fan
- Key Laboratory of Harbor and Marine Structure Durability Technology Ministry of Communications, Guangzhou, 510230, China
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4
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Oswald SW, Aubrey DP. Modeling starch dynamics from seasonal variations of photosynthesis, growth, and respiration. TREE PHYSIOLOGY 2023:tpad007. [PMID: 36708035 DOI: 10.1093/treephys/tpad007] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 11/21/2022] [Indexed: 06/18/2023]
Abstract
Nonstructural carbohydrates (NSCs) buffer differences in plant carbon supply (photosynthesis) and demand (respiration, growth, etc.) but the regulation of their dynamics remains unresolved. Seasonal variations in NSCs are well-documented, but differences in the time-average, amplitude, phase, and other characteristics across ecosystems and functional types lack explanation; furthermore, observed dynamics do not always match expectations. The failure to match observed and expected dynamics has stimulated debate on whether carbon supply or demand drives NSC dynamics. To gain insight into how carbon supply and demand drive seasonal NSC dynamics, we derive a simple model of NSC dynamics based on carbon mass balance and linearizing the NSC demand to determine how supply-driven and demand-driven seasonal NSC dynamics differ. We find that supply-driven and demand-driven dynamics yield distinct timings of seasonal extrema, and supply overrides demand when carbon supply is low in winter (e.g., at high latitudes). Our results also suggest that NSC dynamics often lag changes carbon mass balance. We also predict differences in NSC dynamics across mass, suggesting saplings are more dynamics and respond faster to the environment than mature trees. Our findings suggest substrate-dependent regulation with environmental variation is sufficient to generate complex NSC dynamics.
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Affiliation(s)
- Scott W Oswald
- Savannah River Ecology Lab, Savannah River Site, Jackson, SC, USA
- Warnell School of Forestry, University of Georgia, Athens, GA, USA
| | - Doug P Aubrey
- Savannah River Ecology Lab, Savannah River Site, Jackson, SC, USA
- Warnell School of Forestry, University of Georgia, Athens, GA, USA
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Dominguez PG, Niittylä T. Mobile forms of carbon in trees: metabolism and transport. TREE PHYSIOLOGY 2022; 42:458-487. [PMID: 34542151 PMCID: PMC8919412 DOI: 10.1093/treephys/tpab123] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 07/16/2021] [Accepted: 09/12/2021] [Indexed: 05/26/2023]
Abstract
Plants constitute 80% of the biomass on earth, and almost two-thirds of this biomass is found in wood. Wood formation is a carbon (C)-demanding process and relies on C transport from photosynthetic tissues. Thus, understanding the transport process is of major interest for understanding terrestrial biomass formation. Here, we review the molecules and mechanisms used to transport and allocate C in trees. Sucrose is the major form in which C is transported in plants, and it is found in the phloem sap of all tree species investigated so far. However, in several tree species, sucrose is accompanied by other molecules, notably polyols and the raffinose family of oligosaccharides. We describe the molecules that constitute each of these transport groups, and their distribution across different tree species. Furthermore, we detail the metabolic reactions for their synthesis, the mechanisms by which trees load and unload these compounds in and out of the vascular system, and how they are radially transported in the trunk and finally catabolized during wood formation. We also address a particular C recirculation process between phloem and xylem that occurs in trees during the annual cycle of growth and dormancy. A search of possible evolutionary drivers behind the diversity of C-carrying molecules in trees reveals no consistent differences in C transport mechanisms between angiosperm and gymnosperm trees. Furthermore, the distribution of C forms across species suggests that climate-related environmental factors will not explain the diversity of C transport forms. However, the consideration of C-transport mechanisms in relation to tree-rhizosphere coevolution deserves further attention. To conclude the review, we identify possible future lines of research in this field.
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Affiliation(s)
- Pia Guadalupe Dominguez
- Instituto de Agrobiotecnología y Biología Molecular (IABIMO), Instituto Nacional de Tecnología Agropecuaria (INTA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Hurlingham, Buenos Aires B1686IGC, Argentina
| | - Totte Niittylä
- Department of Forest Genetics and Plant Physiology, Umeå Plant Science Centre, Swedish University of Agricultural Sciences, Umeå 90183, Sweden
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6
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Hikino K, Danzberger J, Riedel VP, Rehschuh R, Ruehr NK, Hesse BD, Lehmann MM, Buegger F, Weikl F, Pritsch K, Grams TEE. High resilience of carbon transport in long-term drought-stressed mature Norway spruce trees within 2 weeks after drought release. GLOBAL CHANGE BIOLOGY 2022; 28:2095-2110. [PMID: 34927319 DOI: 10.1111/gcb.16051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 11/29/2021] [Indexed: 06/14/2023]
Abstract
Under ongoing global climate change, drought periods are predicted to increase in frequency and intensity in the future. Under these circumstances, it is crucial for tree's survival to recover their restricted functionalities quickly after drought release. To elucidate the recovery of carbon (C) transport rates in c. 70-year-old Norway spruce (Picea abies [L.] KARST.) after 5 years of recurrent summer droughts, we conducted a continuous whole-tree 13 C labeling experiment in parallel with watering. We determined the arrival time of current photoassimilates in major C sinks by tracing the 13 C label in stem and soil CO2 efflux, and tips of living fine roots. In the first week after watering, aboveground C transport rates (CTR) from crown to trunk base were still 50% lower in previously drought-stressed trees (0.16 ± 0.01 m h-1 ) compared to controls (0.30 ± 0.06 m h-1 ). Conversely, CTR below ground, that is, from the trunk base to soil CO2 efflux were already similar between treatments (c. 0.03 m h-1 ). Two weeks after watering, aboveground C transport of previously drought-stressed trees recovered to the level of the controls. Furthermore, regrowth of water-absorbing fine roots upon watering was supported by faster incorporation of 13 C label in previously drought-stressed (within 12 ± 10 h upon arrival at trunk base) compared to control trees (73 ± 10 h). Thus, the whole-tree C transport system from the crown to soil CO2 efflux fully recovered within 2 weeks after drought release, and hence showed high resilience to recurrent summer droughts in mature Norway spruce forests. This high resilience of the C transport system is an important prerequisite for the recovery of other tree functionalities and productivity.
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Affiliation(s)
- Kyohsuke Hikino
- Technical University of Munich (TUM), TUM School of Life Sciences, Land Surface-Atmosphere Interactions, Ecophysiology of Plants, Freising, Germany
| | - Jasmin Danzberger
- Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Institute of Biochemical Plant Pathology, Neuherberg, Germany
| | - Vincent P Riedel
- Technical University of Munich (TUM), TUM School of Life Sciences, Land Surface-Atmosphere Interactions, Ecophysiology of Plants, Freising, Germany
| | - Romy Rehschuh
- Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research-Atmospheric Environmental Research (KIT/IMK-IFU), Garmisch-Partenkirchen, Germany
| | - Nadine K Ruehr
- Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research-Atmospheric Environmental Research (KIT/IMK-IFU), Garmisch-Partenkirchen, Germany
| | - Benjamin D Hesse
- Technical University of Munich (TUM), TUM School of Life Sciences, Land Surface-Atmosphere Interactions, Ecophysiology of Plants, Freising, Germany
| | - Marco M Lehmann
- Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Forest Dynamics, Birmensdorf, Switzerland
| | - Franz Buegger
- Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Institute of Biochemical Plant Pathology, Neuherberg, Germany
| | - Fabian Weikl
- Technical University of Munich (TUM), TUM School of Life Sciences, Land Surface-Atmosphere Interactions, Ecophysiology of Plants, Freising, Germany
- Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Institute of Biochemical Plant Pathology, Neuherberg, Germany
| | - Karin Pritsch
- Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Institute of Biochemical Plant Pathology, Neuherberg, Germany
| | - Thorsten E E Grams
- Technical University of Munich (TUM), TUM School of Life Sciences, Land Surface-Atmosphere Interactions, Ecophysiology of Plants, Freising, Germany
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7
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Potkay A, Hölttä T, Trugman AT, Fan Y. Turgor-limited predictions of tree growth, height and metabolic scaling over tree lifespans. TREE PHYSIOLOGY 2022; 42:229-252. [PMID: 34296275 DOI: 10.1093/treephys/tpab094] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Accepted: 07/18/2021] [Indexed: 06/13/2023]
Abstract
Increasing evidence suggests that tree growth is sink-limited by environmental and internal controls rather than by carbon availability. However, the mechanisms underlying sink-limitations are not fully understood and thus not represented in large-scale vegetation models. We develop a simple, analytically solved, mechanistic, turgor-driven growth model (TDGM) and a phloem transport model (PTM) to explore the mechanics of phloem transport and evaluate three hypotheses. First, phloem transport must be explicitly considered to accurately predict turgor distributions and thus growth. Second, turgor-limitations can explain growth-scaling with size (metabolic scaling). Third, turgor can explain realistic growth rates and increments. We show that mechanistic, sink-limited growth schemes based on plant turgor limitations are feasible for large-scale model implementations with minimal computational demands. Our PTM predicted nearly uniform sugar concentrations along the phloem transport path regardless of phloem conductance, stem water potential gradients and the strength of sink-demands contrary to our first hypothesis, suggesting that phloem transport is not limited generally by phloem transport capacity per se but rather by carbon demand for growth and respiration. These results enabled TDGM implementation without explicit coupling to the PTM, further simplifying computation. We test the TDGM by comparing predictions of whole-tree growth rate to well-established observations (site indices) and allometric theory. Our simple TDGM predicts realistic tree heights, growth rates and metabolic scaling over decadal to centurial timescales, suggesting that tree growth is generally sink and turgor limited. Like observed trees, our TDGM captures tree-size- and resource-based deviations from the classical ¾ power-law metabolic scaling for which turgor is responsible.
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Affiliation(s)
- Aaron Potkay
- Department of Earth and Planetary Sciences, Rutgers University, New Brunswick, NJ 08854, USA
| | - Teemu Hölttä
- Institute for Atmospheric and Earth System Research/Forest Sciences, University of Helsinki, Helsinki FI-00014, Finland
| | - Anna T Trugman
- Department of Geography, University of California at Santa Barbara, Santa Barbara, CA 93106, USA
| | - Ying Fan
- Department of Earth and Planetary Sciences, Rutgers University, New Brunswick, NJ 08854, USA
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8
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Li SY, Vincent C. Root:shoot balance controls flush phenology and carbohydrate translocation dynamics in citrus (Citrus x sinensis) trunk. PHYSIOLOGIA PLANTARUM 2022; 174:e13601. [PMID: 34796913 DOI: 10.1111/ppl.13601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 11/01/2021] [Accepted: 11/17/2021] [Indexed: 06/13/2023]
Abstract
Flush shoot growth presents a fluctuation pattern alternating with root growth. The cyclic pattern determines the balance of root:shoot and can affect the direction and speed of carbohydrate translocation during the vegetative growth period. In this study, we used water deficit to limit corresponding growth in sweet orange (Citrus x sinensis) "OLL 4" grafted on "US-942" rootstock, and then observed the changes of translocation dynamics between two flush statuses. Our first hypothesis was that water deficit would reduce root growth and extend the root growth phase during the growth cycle, delaying the following flush. We then tested the related second hypothesis that shoot flushes would switch the direction and slow the speed of carbohydrate transport due to fluctuation between single and dual sinks. After recovery from a severe deficit, the flush was synchronized and emerged within 2 weeks. Mild and moderate water-deficit plants showed a delayed new flush. Next, we used a 14 C-labeling method to test whether translocation was affected by the presence of new flush. Basipetal translocation was dominant, but the new flush increased the likelihood of acropetal translocation. Translocation speeds were not different in both directions regardless of flushing status, though speed estimates were highly variable, even though 14 C export from the source leaf increased when new flush was present. The results suggest that flush timing across an environmental gradient is governed by source-sink dynamics. The presence of new flush altered the direction of photoassimilate translocation and rate of leaf export, but stem transport speeds were not distinguishably different.
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Affiliation(s)
- Sheng-Yang Li
- Horticultural Sciences Department, Citrus Research and Education Center, University of Florida, Lake Alfred, Florida, USA
| | - Christopher Vincent
- Horticultural Sciences Department, Citrus Research and Education Center, University of Florida, Lake Alfred, Florida, USA
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9
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Hotter droughts alter resource allocation to chemical defenses in piñon pine. Oecologia 2021; 197:921-938. [PMID: 34657177 PMCID: PMC8591002 DOI: 10.1007/s00442-021-05058-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Accepted: 10/04/2021] [Indexed: 01/11/2023]
Abstract
Heat and drought affect plant chemical defenses and thereby plant susceptibility to pests and pathogens. Monoterpenes are of particular importance for conifers as they play critical roles in defense against bark beetles. To date, work seeking to understand the impacts of heat and drought on monoterpenes has primarily focused on young potted seedlings, leaving it unclear how older age classes that are more vulnerable to bark beetles might respond to stress. Furthermore, we lack a clear picture of what carbon resources might be prioritized to support monoterpene synthesis under drought stress. To address this, we measured needle and woody tissue monoterpene concentrations and physiological variables simultaneously from mature piñon pines (Pinus edulis) from a unique temperature and drought manipulation field experiment. While heat had no effect on total monoterpene concentrations, trees under combined heat and drought stress exhibited ~ 85% and 35% increases in needle and woody tissue, respectively, over multiple years. Plant physiological variables like maximum photosynthesis each explained less than 10% of the variation in total monoterpenes for both tissue types while starch and glucose + fructose measured 1-month prior explained ~ 45% and 60% of the variation in woody tissue total monoterpene concentrations. Although total monoterpenes increased under combined stress, some key monoterpenes with known roles in bark beetle ecology decreased. These shifts may make trees more favorable for bark beetle attack rather than well defended, which one might conclude if only considering total monoterpene concentrations. Our results point to cumulative and synergistic effects of heat and drought that may reprioritize carbon allocation of specific non-structural carbohydrates toward defense.
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10
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Liesche J, Vincent C, Han X, Zwieniecki M, Schulz A, Gao C, Bravard R, Marker S, Bohr T. The mechanism of sugar export from long conifer needles. THE NEW PHYTOLOGIST 2021; 230:1911-1924. [PMID: 33638181 DOI: 10.1111/nph.17302] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 02/17/2021] [Indexed: 06/12/2023]
Abstract
The green leaves of plants are optimised for carbon fixation and the production of sugars, which are used as central units of carbon and energy throughout the plant. However, there are physical limits to this optimisation that remain insufficiently understood. Here, quantitative anatomical analysis combined with mathematical modelling and sugar transport rate measurements were used to determine how effectively sugars are exported from the needle-shaped leaves of conifers in relation to leaf length. Mathematical modelling indicated that phloem anatomy constrains sugar export in long needles. However, we identified two mechanisms by which this constraint is overcome, even in needles longer than 20 cm: (1) the grouping of transport conduits, and (2) a shift in the diurnal rhythm of sugar metabolism and export in needle tips. The efficiency of sugar transport in the phloem can have a significant influence on leaf function. The constraints on sugar export described here for conifer needles are likely to also be relevant in other groups of plants, such as grasses and angiosperm trees.
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Affiliation(s)
- Johannes Liesche
- College of Life Sciences & Biomass Energy Center for Arid and Semi-arid Lands, Northwest A&F University, Taicheng Road 3, Yangling, 712100, China
- Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, Düsseldorf, 40225, Germany
| | - Christopher Vincent
- Department of Horticultural Sciences, University of Florida, 700 Experiment Station Road, Lake Alfred, FL, 33850, USA
| | - Xiaoyu Han
- College of Life Sciences & Biomass Energy Center for Arid and Semi-arid Lands, Northwest A&F University, Taicheng Road 3, Yangling, 712100, China
| | - Maciej Zwieniecki
- Department of Plant Sciences, University of California, Davis One Shields Avenue, Davis, CA, 95616, USA
| | - Alexander Schulz
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg, 1871, Denmark
| | - Chen Gao
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg, 1871, Denmark
| | - Rodrigue Bravard
- Department of Physics, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark
| | - Sean Marker
- Department of Physics, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark
| | - Tomas Bohr
- Department of Physics, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark
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11
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Rodríguez-Calcerrada J, Rodrigues AM, António C, Perdiguero P, Pita P, Collada C, Li M, Gil L. Stem metabolism under drought stress - a paradox of increasing respiratory substrates and decreasing respiratory rates. PHYSIOLOGIA PLANTARUM 2021; 172:391-404. [PMID: 32671841 DOI: 10.1111/ppl.13145] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 05/25/2020] [Accepted: 05/28/2020] [Indexed: 06/11/2023]
Abstract
Metabolic changes underpinning drought-induced variations in stem respiration (Rs ) are unknown. We measured Rs rates and metabolite and gene expression profiles in Ulmus minor Mill. and Quercus ilex L. seedlings subjected to increasing levels of drought stress to better understand how carbon, nitrogen and energy metabolism interact during drought. In both species, only plants showing extreme stress symptoms - i.e. negligible rates of leaf stomatal conductance and photosynthesis, and high stem dehydration (30-50% of maximum water storage) and contraction (50-150 μm week-1 ) - exhibited lower Rs rates than well-watered plants. Abundance of low-molecular weight sugars (e.g. glucose and fructose) and sugar alcohols (e.g. mannitol) increased with drought, at more moderate stress and to a higher extent in Q. ilex than U. minor. Abundance of amino acids increased at more severe stress, more abruptly, and to a higher extent in U. minor, coinciding with leaf senescence, which did not occur in Q. ilex. Organic acids changed less in response to drought: threonate and glycerate increased, and citrate decreased although slightly in both species. Transcripts of genes coding for enzymes of the Krebs cycle decreased in Q. ilex and increased in U. minor in conditions of extreme drought stress. The maintenance of Rs under severe growth and photosynthetic restrictions reveals the importance of stem mitochondrial activity in drought acclimation. The eventual decline in Rs diverts carbon substrates from entering the Krebs cycle that may help to cope with osmotic and oxidative stress during severe drought and to recover hydraulic functionality afterwards.
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Affiliation(s)
- Jesús Rodríguez-Calcerrada
- Grupo de Investigación Sistemas Naturales e Historia Forestal, Universidad Politécnica de Madrid, Madrid, 28040, Spain
| | - Ana M Rodrigues
- Plant Metabolomics Laboratory, Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB NOVA), Oeiras, 2780-157, Portugal
| | - Carla António
- Plant Metabolomics Laboratory, Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB NOVA), Oeiras, 2780-157, Portugal
| | - Pedro Perdiguero
- Animal Health Research Center, National Institute for Agriculture and Food Research and Technology (CISA-INIA), Valdeolmos, Madrid, 28130, Spain
| | - Pilar Pita
- Grupo de Investigación Sistemas Naturales e Historia Forestal, Universidad Politécnica de Madrid, Madrid, 28040, Spain
| | - Carmen Collada
- Grupo de Investigación Sistemas Naturales e Historia Forestal, Universidad Politécnica de Madrid, Madrid, 28040, Spain
| | - Meng Li
- Grupo de Investigación Sistemas Naturales e Historia Forestal, Universidad Politécnica de Madrid, Madrid, 28040, Spain
| | - Luis Gil
- Grupo de Investigación Sistemas Naturales e Historia Forestal, Universidad Politécnica de Madrid, Madrid, 28040, Spain
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12
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Hammond WM, Johnson DM, Meinzer FC. A thin line between life and death: Radial sap flux failure signals trajectory to tree mortality. PLANT, CELL & ENVIRONMENT 2021; 44:1311-1314. [PMID: 33600002 DOI: 10.1111/pce.14033] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 02/12/2021] [Accepted: 02/13/2021] [Indexed: 06/12/2023]
Abstract
This article comments on: Seeking the "point of no return" in the sequence of events leading to mortality of mature trees.
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Affiliation(s)
- William M Hammond
- Department of Plant Biology, Ecology, and Evolution, Oklahoma State University, Stillwater, Oklahoma, USA
| | - Daniel M Johnson
- Warnell School of Forestry and Natural Resources, University of Georgia, Athens, Georgia, USA
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13
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Guo X, Peng C, Li T, Huang J, Song H, Zhu Q, Wang M. The Effects of Drought and Re-Watering on Non-Structural Carbohydrates of Pinus tabulaeformis Seedlings. BIOLOGY 2021; 10:biology10040281. [PMID: 33808347 PMCID: PMC8066268 DOI: 10.3390/biology10040281] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 03/24/2021] [Accepted: 03/26/2021] [Indexed: 11/24/2022]
Abstract
Simple Summary Drought is one of the main drivers resulting in carbon imbalance in terrestrial ecosystems and the mortality of plants. How plants can survive under drought stress is becoming a major focus of interest. Non-structural carbohydrates include sugars and starch that are essential to plant metabolism and their roles in drought stress are thought to be critically important. Our study examined the allocation strategies of non-structural carbohydrates for three-year-old Pinus tabulaeformis (Chinese pine) seedlings under drought and subsequent re-watering conditions. Our results indicated that P. tabulaeformis seedlings showed strong drought resistance by investing limited non-structural carbohydrates to roots and depleting the starch storage in each organ (leaf, twig, stem, and root) to fuel the needs of plant metabolism and osmotic adjustment. Starch storage was first reconstructed after the drought stress was released. Our findings not only prove the important role of non-structural carbohydrates, especially starch storage, in the survival of P. tabulaeformis seedlings under drought condition, but also complement the limited studies on allocation strategies of non-structural carbohydrate after the drought stress is released, and broaden our understanding of the physiological mechanisms of plants in response to drought stress. Abstract Intense and frequent drought events strongly affect plant survival. Non-structural carbohydrates (NSCs) are important “buffers” to maintain plant functions under drought conditions. We conducted a drought manipulation experiment using three-year-old Pinus tabulaeformis Carr. seedlings. The seedlings were first treated under different drought intensities (i.e., no irrigation, severe, and moderate) for 50 days, and then they were re-watered for 25 days to explore the dynamics of NSCs in the leaves, twigs, stems, and roots. The results showed that the no irrigation and severe drought treatments significantly reduced photosynthetic rate by 93.9% and 32.6% for 30 days, respectively, leading to the depletion of the starch storage for hydraulic repair, osmotic adjustment, and plant metabolism. The seedlings under moderate drought condition also exhibited starch storage consumption in leaves and twigs. After re-watering, the reduced photosynthetic rate recovered to the control level within five days in the severe drought group but showed no sign of recovery in the no irrigation group. The seedlings under the severe and moderate drought conditions tended to invest newly fixed C to starch storage and hydraulic repair instead of growth due to the “drought legacy effect”. Our findings suggest the depletion and recovery of starch storage are important strategies for P. tabulaeformis seedlings, and they may play key roles in plant resistance and resilience under environmental stress.
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Affiliation(s)
- Xinyi Guo
- Center for Ecological Forecasting and Global Change, College of Forestry, Northwest A&F University, Yangling 712100, China; (X.G.); (T.L.); (J.H.)
| | - Changhui Peng
- Center for Ecological Forecasting and Global Change, College of Forestry, Northwest A&F University, Yangling 712100, China; (X.G.); (T.L.); (J.H.)
- Department of Biology Sciences, Institute of Environment Sciences, University of Quebec at Montreal, P.O. Box 8888, Station Centre-Ville, Montreal, QC H3C 3P8, Canada;
- Correspondence: (C.P.); (M.W.)
| | - Tong Li
- Center for Ecological Forecasting and Global Change, College of Forestry, Northwest A&F University, Yangling 712100, China; (X.G.); (T.L.); (J.H.)
| | - Jingjing Huang
- Center for Ecological Forecasting and Global Change, College of Forestry, Northwest A&F University, Yangling 712100, China; (X.G.); (T.L.); (J.H.)
| | - Hanxiong Song
- Department of Biology Sciences, Institute of Environment Sciences, University of Quebec at Montreal, P.O. Box 8888, Station Centre-Ville, Montreal, QC H3C 3P8, Canada;
| | - Qiuan Zhu
- College of Hydrology and Water Resources, Hohai University, Nanjing 210098, China;
| | - Meng Wang
- Key Laboratory of Geographical Processes and Ecological Security in Changbai Mountains, Ministry of Education, School of Geographical Sciences, Northeast Normal University, Changchun 130024, China
- State Environmental Protection Key Laboratory of Wetland Ecology and Vegetation Restoration, Institute for Peat and Mire Research, Northeast Normal University, Changchun 130024, China
- Jilin Provincial Key Laboratory for Wetland Ecological Processes and Environmental Change in the Changbai Mountains, Changchun 130024, China
- Correspondence: (C.P.); (M.W.)
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14
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Abstract
When developing theories, designing studies, and interpreting the results, researchers are influenced by their perception of tree size. For example, we may compare two trees of the same size belonging to different species, and attribute any differences to dissimilarities between the species. However, the meaning of “same size” depends on the measures of size used. Wood density influences certain measures, such as biomass, but does not influence e.g., trunk diameter. Therefore, the choice of the measure of size can reverse any conclusions. Hence, it is import to consider which measure of size should be used. I argue that the most common measure of size, i.e., trunk diameter, is often a bad choice when wood density varies, as diameter is then not directly related to processes important in evolution. When trees with equal diameters but differing wood densities are compared, the tree with denser wood is larger if the measure of size is related to construction cost or trunk strength, a proxy of leaf area. From this perspective, the comparison is then conducted between a biologically larger heavy-wooded tree and a smaller light-wooded tree, and the differences between the trees may be caused by size instead of wood density. Therefore, trunk biomass and strength may often be more suitable measures of size, as they reflect the construction cost and biomechanical potency linked to leaf area crown height, often too challenging to estimate more directly. To assess how commonly inadequate measures of tree size have been used, I reviewed 10 highly cited journal articles. None of these 10 articles discussed the impact of wood density on biological size, and instead based the analyses on diameters or basal areas. This led to conclusions that could change or even reverse in an analysis based on biomass or strength. Overall, I do not suggest avoiding the use of diameter, but I recommend considering result sensitivity to the measure of size, particularly in studies ones with variable wood densities.
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15
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Kannenberg SA, Phillips RP. Non-structural carbohydrate pools not linked to hydraulic strategies or carbon supply in tree saplings during severe drought and subsequent recovery. TREE PHYSIOLOGY 2020; 40:259-271. [PMID: 31860721 DOI: 10.1093/treephys/tpz132] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 10/30/2019] [Accepted: 11/16/2019] [Indexed: 06/10/2023]
Abstract
Non-structural carbohydrate (NSC) pools fluctuate based on the interplay between photosynthesis, demand from various carbon (C) sinks and tree hydraulic status. Thus, it has been hypothesized that tree species with isohydric stomatal control (i.e., trees that close stomata rapidly in response to drought) rely heavily on NSC pools to sustain metabolism, which can lead to negative physiological consequences such as C depletion. Here, we seek to use a species' degree of isohydry or anisohydry as a conceptual framework for understanding the interrelations between photosynthetic C supply, hydraulic damage and fluctuations in NSC pools. We conducted a 6-week experimental drought, followed by a 6-week recovery period, in a greenhouse on seven tree species that span the spectrum from isohydric to anisohydric. Throughout the experiment, we measured photosynthesis, hydraulic damage and NSC pools. Non-structural carbohydrate pools were remarkably stable across species and tissues-even highly isohydric species that drastically reduced C assimilation were able to maintain stored C. Despite these static NSC pools, we still inferred an important role for stored C during drought, as most species converted starches into sugars during water stress (and back again post-drought). Finally, we did not observe any linkages between C supply, hydraulic damage and NSC pools, indicating that NSC was maintained independent of variation in photosynthesis and hydraulic function. Our results advance the idea that C depletion is a rare phenomenon due to either active maintenance of NSC pools or sink limitation, and thus question the hypothesis that reductions in C assimilation necessarily lead to C depletion.
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Affiliation(s)
- Steven A Kannenberg
- School of Biological Sciences, University of Utah, 257 1400 East, Salt Lake City, UT 84112, USA
- Department of Biology, Indiana University, 1001 East 3rd Street, Bloomington, IN 47405, USA
| | - Richard P Phillips
- Department of Biology, Indiana University, 1001 East 3rd Street, Bloomington, IN 47405, USA
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16
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Hillabrand RM, Hacke UG, Lieffers VJ. Defoliation constrains xylem and phloem functionality. TREE PHYSIOLOGY 2019; 39:1099-1108. [PMID: 30901057 DOI: 10.1093/treephys/tpz029] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 03/07/2019] [Indexed: 06/09/2023]
Abstract
Insect defoliation contributes to tree mortality under drought conditions. Defoliation-induced alterations to the vascular transport structure may increase tree vulnerability to drought; however, this has been rarely studied. To evaluate the response of tree vascular function following defoliation, 2-year-old balsam poplar were manually defoliated, and both physiological and anatomical measurements were made after allowing for re-foliation. Hydraulic conductivity measurements showed that defoliated trees had both increased vulnerability to embolism and decreased water transport efficiency, likely due to misshapen xylem vessels. Anatomical measurements revealed novel insights into defoliation-induced alterations to the phloem. Phloem sieve tube diameter was reduced in the stems of defoliated trees, suggesting reduced transport capability. In addition, phloem fibers were absent, or reduced in number, in stems, shoot tips and petioles of new leaves, potentially reducing the stability of the vascular tissue. Results from this study suggest that the defoliation leads to trees with increased risk for vascular dysfunction and drought-induced mortality through alterations in the vascular structure, and highlights a route through which carbon limitation can influence hydraulic dysfunction.
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Affiliation(s)
- Rachel M Hillabrand
- Department of Renewable Resources, University of Alberta, 442 Earth Sciences Building, Edmonton, AB, Canada
| | - Uwe G Hacke
- Department of Renewable Resources, University of Alberta, 442 Earth Sciences Building, Edmonton, AB, Canada
| | - Victor J Lieffers
- Department of Renewable Resources, University of Alberta, 442 Earth Sciences Building, Edmonton, AB, Canada
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17
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Sevanto S. Methods for Assessing the Role of Phloem Transport in Plant Stress Responses. Methods Mol Biol 2019; 2014:311-336. [PMID: 31197806 DOI: 10.1007/978-1-4939-9562-2_25] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
Delivery of carbohydrates to tissues that need them under stress is important for plant defenses and survival. Yet, little is known on how phloem function is altered under stress, and how that influences plant responses to stress. This is because phloem is a challenging tissue to study. It consists of cells of various types with soft cell walls, and the cells show strong wounding reactions to protect their integrity, making both imaging and functional studies challenging. This chapter summarizes theories on how phloem transport is affected by stress and presents methods that have been used to gain the current knowledge. These techniques range from tracer studies and imaging to carbon balance and anatomical analyses. Advances in these techniques in the recent years have considerably increased our ability to investigate phloem function, and application of the new methods on plant stress studies will help provide a more comprehensive picture of phloem function and its limitations under stress.
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Affiliation(s)
- Sanna Sevanto
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
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18
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Dynamic Simulation of the Crown Net Photosynthetic Rate for Young Larix olgensis Henry Trees. FORESTS 2019. [DOI: 10.3390/f10040321] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Numerical integration of the instantaneous net photosynthetic rate (An) is a common method for calculating the long-term CO2 uptake of trees, and accurate dynamic simulation of the crown An has been receiving substantial attention. Tree characteristics are challenging to assess given their aerodynamically coarse crown properties, spatiotemporal variation in leaf functional traits and microenvironments. Therefore, the variables associated with the dynamic variations in the crown An must be identified. The relationships of leaf temperature (Tleaf), the vapor pressure deficit (VPD), leaf mass per area (LMA) and the relative depth into the crown (RDINC) with the parameters of the photosynthetic light-response (PLR) model of Larix olgensis Henry were analyzed. The LMA, RDINC and VPD were highly correlated with the maximum net photosynthetic rate (Amax). The VPD was the key variable that mainly determined the variation in the apparent quantum yield (AQY). Tleaf exhibited a significant exponential correlation with the dark respiration rate (Rd). According to the above correlations, the crown PLR model of L. olgensis trees was constructed by linking VPD, LMA and RDINC to the original PLR equation. The model performed well, with a high coefficient of determination (R2) value (0.883) and low root mean square error (RMSE) value (1.440 μmol m−2 s−1). The extinction coefficient (k) of different pseudowhorls within a crown was calculated by the Beer–Lambert equation based on the observed photosynthetically active radiation (PAR) distribution. The results showed that k was not a constant value but varied with the RDINC, solar elevation angle (ψ) and cumulative leaf area of the whole crown (CLA). Thus, we constructed a k model by reparameterizing the power function of RDINC with the ψ and CLA, and the PAR distribution within a crown was therefore well estimated (R2 = 0.698 and RMSE = 174.4 μmol m−2 s−1). Dynamic simulation of the crown An for L. olgensis trees was achieved by combining the crown PLR model and dynamic PAR distribution model. Although the models showed some weakened physiological biochemical processes during photosynthesis, they enabled the estimation of long-term CO2 uptake for an L. olgensis plantation, and the results could be easily fitted to gas-exchange measurements.
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19
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Wang J, Villar-Salvador P, Li G, Liu Y. Moderate water stress does not inhibit nitrogen remobilization, allowing fast growth in high nitrogen content Quercus variabilis seedlings under dry conditions. TREE PHYSIOLOGY 2019; 39:650-660. [PMID: 30551133 DOI: 10.1093/treephys/tpy130] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 10/11/2018] [Accepted: 11/27/2018] [Indexed: 06/09/2023]
Abstract
Remobilization of stored nitrogen (N) plays an important role in the early growth of deciduous trees in spring. Several environmental factors can modulate N remobilization, but whether water stress is one such factors is unknown. This study analyzes how the size of N storage in Quercus variabilis Blume seedlings interacts with water stress to affect N remobilization, uptake and new growth. This information is important for improving success of forest tree plantations under dry spring conditions. During the first growing season, we produced seedlings with distinct N content by applying two fall N fertilization rates (12 or 24 mg N per seedling) using 15N-enriched fertilizer. At the beginning of the second growing season, a new experiment was started where seedlings were transplanted into larger pots and subjected to two watering levels (85 or 40% of field capacity). The plants were sampled at 4 weeks (T1), 8 weeks (T2) and 12 weeks (T3) after transplanting. Low watering reduced the growth of high and low N seedlings, but high N seedlings showed greater growth than low N seedlings. During bud burst and initial shoot elongation (T1), restricted watering, which induced a moderate water stress, did not affect the amount of N remobilized from roots, the major source of stored N source at this growth stage. This suggests that high N storage can partially counteract the negative effect of moderate water stress on early growth. At T1, water stress did not affect N uptake, and high N content seedlings absorbed significantly less soil N than did low N content seedlings. At T3, in contrast, water stress was the main determinant for N uptake, with drought-stressed plants showing lower uptake than well-watered plants. We conclude that moderate drought does not inhibit N remobilization from the major storage organ at early growth stages in spring, and that increasing N storage of planted seedlings through fall fertilization can mitigate the negative effect of moderate spring drought on growth.
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Affiliation(s)
- Jiaxi Wang
- Key Laboratory for Silviculture and Conservation, Ministry of Education, Beijing Forestry University, Beijing, China
- Beijing Laboratory of Urban and Rural Ecological Environment, Beijing, China
- Key Laboratory for Silviculture and Forest Ecosystem in Arid and Semi-arid Area of State Forestry Administration, Beijing, China
| | - Pedro Villar-Salvador
- Forest Ecology and Restoration Group, Departamento de Ciencias de la Vida, Universidad de Alcalá, Alcalá de Henares, Madrid, Spain
| | - Guolei Li
- Key Laboratory for Silviculture and Conservation, Ministry of Education, Beijing Forestry University, Beijing, China
- Beijing Laboratory of Urban and Rural Ecological Environment, Beijing, China
- Key Laboratory for Silviculture and Forest Ecosystem in Arid and Semi-arid Area of State Forestry Administration, Beijing, China
| | - Yong Liu
- Key Laboratory for Silviculture and Conservation, Ministry of Education, Beijing Forestry University, Beijing, China
- Key Laboratory for Silviculture and Forest Ecosystem in Arid and Semi-arid Area of State Forestry Administration, Beijing, China
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20
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Epron D, Dannoura M, Ishida A, Kosugi Y. Estimation of phloem carbon translocation belowground at stand level in a hinoki cypress stand. TREE PHYSIOLOGY 2019; 39:320-331. [PMID: 29474703 DOI: 10.1093/treephys/tpy016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 01/15/2018] [Accepted: 01/27/2018] [Indexed: 06/08/2023]
Abstract
At stand level, carbon translocation in tree stems has to match canopy photosynthesis and carbohydrate requirements to sustain growth and the physiological activities of belowground sinks. This study applied the Hagen-Poiseuille equation to the pressure-flow hypothesis to estimate phloem carbon translocation and evaluate what percentage of canopy photosynthate can be transported belowground in a hinoki cypress (Chamaecyparis obtusa Sieb. et Zucc.) stand. An anatomical study revealed that, in contrast to sieve cell density, conductive phloem thickness and sieve cell hydraulic diameter at 1.3 m in height increased with increasing tree diameter, as did the concentration of soluble sugars in the phloem sap. At tree level, hydraulic conductivity increased by two orders of magnitude from the smallest to the largest trees in the stand, resulting in a stand-level hydraulic conductance of 1.7 × 10-15 m Pa-1 s-1. The osmotic potential of the sap extracted from the inner bark was -0.75 MPa. Assuming that phloem water potential equalled foliage water potential at predawn, the turgor pressure in the phloem at 1.3 m in height was estimated at 0.22 MPa, 0.59 MPa lower than values estimated in the foliage. With this maximal turgor pressure gradient, which would be lower during day-time when foliage water potential drops, the estimated stand-level rate of carbon translocation was 2.0 gC m-2 day-1 (30% of daily gross canopy photosynthesis), at a time of the year when aboveground growth and related respiration is thought to consume a large fraction of photosynthate, at the expense of belowground activity. Despite relying on some assumptions and approximations, this approach, when coupled with measurements of canopy photosynthesis, may further be used to provide qualitative insight into the seasonal dynamics of belowground carbon allocation.
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Affiliation(s)
- Daniel Epron
- Université de Lorraine, INRA, UMR SILVA, Faculté des Sciences et Technologies, Vandœuvre-lès-Nancy, France
- Kyoto University, Laboratory of Ecosystem Production and Dynamics, Graduate School of Global Environmental Studies, Kyoto, Japan
| | - Masako Dannoura
- Kyoto University, Laboratory of Ecosystem Production and Dynamics, Graduate School of Global Environmental Studies, Kyoto, Japan
- Kyoto University, Laboratory of Forest Utilization, Graduate School of Agriculture, Kyoto, Japan
| | - Atsushi Ishida
- Kyoto University, Center for Ecological Research, Otsu, Shiga, Japan
| | - Yoshiko Kosugi
- Kyoto University, Laboratory of Forest Hydrology, Graduate School of Agriculture, Kyoto, Japan
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21
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Hesse BD, Goisser M, Hartmann H, Grams TEE. Repeated summer drought delays sugar export from the leaf and impairs phloem transport in mature beech. TREE PHYSIOLOGY 2019; 39:192-200. [PMID: 30388272 DOI: 10.1093/treephys/tpy122] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 09/07/2018] [Accepted: 10/05/2018] [Indexed: 05/24/2023]
Abstract
Phloem sustains maintenance and growth processes through transport of sugars from source to sink organs. Under low water availability, tree functioning is impaired, i.e., growth/photosynthesis decline and phloem transport may be hindered. In a 3-year throughfall exclusion (TE) experiment on mature European beech (Fagus sylvatica L.) we conducted 13CO2 branch labeling to investigate translocation of recently fixed photoassimilates under experimental drought over 2 years (2015 and 2016). We hypothesized (H1) that mean residence time of photoassimilates in leaves (MRT) increases, whereas (H2) phloem transport velocity (Vphloem) decreases under drought. Transport of carbohydrates in the phloem was assessed via δ13C of CO2 efflux measured at two branch positions following 13CO2 labeling. Pre-dawn water potential (ΨPD) and time-integrated soil water deficit (iSWD) were used to quantify drought stress. The MRT increased by 46% from 32.1 ± 5.4 h in control (CO) to 46.9 ± 12.3 h in TE trees, supporting H1, and positively correlated (P < 0.001) with iSWD. Confirming H2, Vphloem in 2016 decreased by 47% from 20.7 ± 5.8 cm h-1 in CO to 11.0 ± 2.9 cm h-1 in TE trees and positively correlated with ΨPD (P = 0.001). We suggest that the positive correlation between MRT and iSWD is a result of the accumulation of osmolytes maintaining cell turgor in the leaves under longer drought periods. Furthermore, we propose that the positive correlation between Vphloem and ΨPD is due to a lower water uptake of phloem conduits from surrounding tissues under increasing drought leading to a higher phloem sap viscosity and lower Vphloem. The two mechanisms increasing MRT and reducing Vphloem respond differently to low water availability and impair trees' carbon translocation under drought.
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Affiliation(s)
- Benjamin D Hesse
- Technical University of Munich, Department of Ecology and Ecosystem Management - Chair for Ecophysiology of Plants, Hans-Carl-von-Carlowitz Platz 2, Freising, Germany
| | - Michael Goisser
- Technical University of Munich, Department of Ecology and Ecosystem Management - Chair for Ecophysiology of Plants, Hans-Carl-von-Carlowitz Platz 2, Freising, Germany
| | - Henrik Hartmann
- Max-Planck Institute for Biogeochemistry, Department of Biogeochemical Processes, Hans Knöll Str. 10, Jena, Germany
| | - Thorsten E E Grams
- Technical University of Munich, Department of Ecology and Ecosystem Management - Chair for Ecophysiology of Plants, Hans-Carl-von-Carlowitz Platz 2, Freising, Germany
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22
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Salmon Y, Dietrich L, Sevanto S, Hölttä T, Dannoura M, Epron D. Drought impacts on tree phloem: from cell-level responses to ecological significance. TREE PHYSIOLOGY 2019; 39:173-191. [PMID: 30726983 DOI: 10.1093/treephys/tpy153] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 12/03/2018] [Accepted: 01/25/2019] [Indexed: 06/09/2023]
Abstract
On-going climate change is increasing the risk of drought stress across large areas worldwide. Such drought events decrease ecosystem productivity and have been increasingly linked to tree mortality. Understanding how trees respond to water shortage is key to predicting the future of ecosystem functions. Phloem is at the core of the tree functions, moving resources such as non-structural carbohydrates, nutrients, and defence and information molecules across the whole plant. Phloem function and ability to transport resources is tightly controlled by the balance of carbon and water fluxes within the tree. As such, drought is expected to impact phloem function by decreasing the amount of available water and new photoassimilates. Yet, the effect of drought on the phloem has received surprisingly little attention in the last decades. Here we review existing knowledge on drought impacts on phloem transport from loading and unloading processes at cellular level to possible effects on long-distance transport and consequences to ecosystems via ecophysiological feedbacks. We also point to new research frontiers that need to be explored to improve our understanding of phloem function under drought. In particular, we show how phloem transport is affected differently by increasing drought intensity, from no response to a slowdown, and explore how severe drought might actually disrupt the phloem transport enough to threaten tree survival. Because transport of resources affects other organisms interacting with the tree, we also review the ecological consequences of phloem response to drought and especially predatory, mutualistic and competitive relations. Finally, as phloem is the main path for carbon from sources to sink, we show how drought can affect biogeochemical cycles through changes in phloem transport. Overall, existing knowledge is consistent with the hypotheses that phloem response to drought matters for understanding tree and ecosystem function. However, future research on a large range of species and ecosystems is urgently needed to gain a comprehensive understanding of the question.
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Affiliation(s)
- Yann Salmon
- Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, Gustaf Hällströmin katu 2b, University of Helsinki, Helsinki, Finland
- Institute for Atmospheric and Earth System Research/Forest Sciences, Faculty of Agriculture and Forestry, Latokartanonkaari 7, University of Helsinki, Helsinki, Finland
| | - Lars Dietrich
- Department of Environmental Sciences, University of Basel, Schönbeinstrasse 6, Basel, Switzerland
| | - Sanna Sevanto
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, PO Box 1663 MA 495, Los Alamos, NM, USA
| | - Teemu Hölttä
- Institute for Atmospheric and Earth System Research/Forest Sciences, Faculty of Agriculture and Forestry, Latokartanonkaari 7, University of Helsinki, Helsinki, Finland
| | - Masako Dannoura
- Kyoto University, Laboratory of Ecosystem Production and Dynamics, Graduate School of Global Environmental Studies, Kyoto, Japan
- Kyoto University, Laboratory of Forest Utilization, Graduate School of Agriculture, Kyoto, Japan
| | - Daniel Epron
- Université de Lorraine, AgroParisTech, INRA, UMR Silva, Faculté des Sciences et Technologies, Nancy, France
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23
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Dannoura M, Epron D, Desalme D, Massonnet C, Tsuji S, Plain C, Priault P, Gérant D. The impact of prolonged drought on phloem anatomy and phloem transport in young beech trees. TREE PHYSIOLOGY 2019; 39:201-210. [PMID: 29931112 DOI: 10.1093/treephys/tpy070] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 05/04/2018] [Accepted: 05/18/2018] [Indexed: 06/08/2023]
Abstract
Phloem failure has recently been recognized as one of the mechanisms causing tree mortality under drought, though direct evidence is still lacking. We combined 13C pulse-labelling of 8-year-old beech trees (Fagus sylvatica L.) growing outdoors in a nursery with an anatomical study of the phloem tissue in their stems to examine how drought alters carbon transport and phloem transport capacity. For the six trees under drought, predawn leaf water potential ranged from -0.7 to -2.4 MPa, compared with an average of -0.2 MPa in five control trees with no water stress. We also observed a longer residence time of excess 13C in the foliage and the phloem sap in trees under drought compared with controls. Compared with controls, excess 13C in trunk respiration peaked later in trees under moderate drought conditions and showed no decline even after 4 days under more severe drought conditions. We estimated higher phloem sap viscosity in trees under drought. We also observed much smaller sieve-tube radii in all drought-stressed trees, which led to lower sieve-tube conductivity and lower phloem conductance in the tree stem. We concluded that prolonged drought affected phloem transport capacity through a change in anatomy and that the slowdown of phloem transport under drought likely resulted from a reduced driving force due to lower hydrostatic pressure between the source and sink organs.
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Affiliation(s)
- Masako Dannoura
- Université de Lorraine, AgroParisTech, INRA, UMR Silva, Faculté des Sciences et Technologies, Nancy, France
- Laboratory of Ecosystem Production and Dynamics, Graduate School of Global Environmental Studies, Kyoto University, Kyoto, Japan
- Laboratory of Forest Utilization, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Daniel Epron
- Université de Lorraine, AgroParisTech, INRA, UMR Silva, Faculté des Sciences et Technologies, Nancy, France
| | - Dorine Desalme
- Université de Lorraine, AgroParisTech, INRA, UMR Silva, Faculté des Sciences et Technologies, Nancy, France
| | - Catherine Massonnet
- Université de Lorraine, AgroParisTech, INRA, UMR Silva, Faculté des Sciences et Technologies, Nancy, France
| | - Shoko Tsuji
- Laboratory of Ecosystem Production and Dynamics, Graduate School of Global Environmental Studies, Kyoto University, Kyoto, Japan
| | - Caroline Plain
- Université de Lorraine, AgroParisTech, INRA, UMR Silva, Faculté des Sciences et Technologies, Nancy, France
| | - Pierrick Priault
- Université de Lorraine, AgroParisTech, INRA, UMR Silva, Faculté des Sciences et Technologies, Nancy, France
| | - Dominique Gérant
- Université de Lorraine, AgroParisTech, INRA, UMR Silva, Faculté des Sciences et Technologies, Nancy, France
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Epron D, Dannoura M, Hölttä T. Introduction to the invited issue on phloem function and dysfunction. TREE PHYSIOLOGY 2019; 39:167-172. [PMID: 30785633 DOI: 10.1093/treephys/tpz007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 01/08/2019] [Accepted: 01/15/2019] [Indexed: 06/09/2023]
Affiliation(s)
- Daniel Epron
- Université de Lorraine, AgroParisTech, INRA, UMR Silva, Faculté des Sciences et Technologies, Nancy, France
| | - Masako Dannoura
- Kyoto University, Laboratory of Ecosystem Production and Dynamics, Graduate School of Global Environmental Studies, Kyoto, Japan
- Kyoto University, Laboratory of Forest Utilization, Graduate School of Agriculture, Kyoto, Japan
| | - Teemu Hölttä
- Institute for Atmospheric and Earth System Research/Forest Sciences, Faculty of Agriculture and Forestry, Latokartanonkaari 7, University of Helsinki, Helsinki, Finland
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25
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Spatial and Seasonal Variations of Standardized Photosynthetic Parameters under Different Environmental Conditions for Young Planted Larix olgensis Henry Trees. FORESTS 2018. [DOI: 10.3390/f9090522] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Understanding the spatial and seasonal variations in leaf physiology is critical for accurately modeling the carbon uptake, physiological processes and growth of entire canopies and stands. For a 17-year-old Larix olgensis Henry plantation, vertical whorl-by-whorl sampling and analyses of seasonally repeated measurements of major photosynthetic parameters were conducted, and the correlations between photosynthetic parameters and environmental conditions, leaf morphological traits and spatial position within the crown were analyzed. According to the correlations, the photosynthetic parameters were standardized based on the environmental conditions to avoid the influence of the changing environment on the patterns of spatial and seasonal variations of photosynthetic parameters. The results showed that the standardized light-saturated net photosynthetic rate (SPmax), standardized dark respiration (SRd) and standardized stomatal conductance under saturated light (Sgs-sat) were all negatively related to the relative depth into the crown (RDINC) throughout the growing season. However, their vertical patterns were different during the development of the phenological phase. In addition, different gradients of environmental conditions also influenced the values and the range of the vertical variation in photosynthesis. High temperature and low humidity usually resulted in smaller values and weaker vertical variations of SPmax and Sgs-sat, but larger values and more obvious vertical variations in SRd. SPmax and Sgs-sat usually exhibited a parabolic seasonal pattern in different vertical positions within the crown; however, SRd generally followed a concave pattern. These seasonal patterns were all weaker with increasing RDINC. Different environments also exhibited a significant influence on the seasonal patterns of photosynthesis. We suggested that standardization is necessary before analyzing spatial and seasonal variations. A single environmental condition could not represent the spatial and seasonal patterns under all gradients of the environment. Spatial and seasonal variations should be simultaneously analyzed because they are related to each other.
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26
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Sevanto S. Drought impacts on phloem transport. CURRENT OPINION IN PLANT BIOLOGY 2018; 43:76-81. [PMID: 29448177 DOI: 10.1016/j.pbi.2018.01.002] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2017] [Revised: 01/03/2018] [Accepted: 01/13/2018] [Indexed: 05/27/2023]
Abstract
Drought impacts on phloem transport have attracted attention only recently, despite the well-established, and empirically verified theories on drought impacts on water transport in plants in general. This is because studying phloem transport is challenging. Phloem tissue is relatively small and delicate, and it has often been assumed not to be impacted by drought, or having insignificant impact on plant function or survival compared to the xylem. New evidence, however, suggests that drought responses of the phloem might hold the key for predicting plant survival time during drought or revival capacity after drought. This review summarizes current theories and empirical evidence on how drought might impact phloem transport, and evaluates these findings in relation to plant survival during drought.
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Affiliation(s)
- Sanna Sevanto
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, PO Box 1663, Los Alamos, NM 87545, USA.
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27
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Johnson DM, Domec JC, Carter Berry Z, Schwantes AM, McCulloh KA, Woodruff DR, Wayne Polley H, Wortemann R, Swenson JJ, Scott Mackay D, McDowell NG, Jackson RB. Co-occurring woody species have diverse hydraulic strategies and mortality rates during an extreme drought. PLANT, CELL & ENVIRONMENT 2018; 41:576-588. [PMID: 29314069 DOI: 10.1111/pce.13121] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 12/01/2017] [Indexed: 05/25/2023]
Abstract
From 2011 to 2013, Texas experienced its worst drought in recorded history. This event provided a unique natural experiment to assess species-specific responses to extreme drought and mortality of four co-occurring woody species: Quercus fusiformis, Diospyros texana, Prosopis glandulosa, and Juniperus ashei. We examined hypothesized mechanisms that could promote these species' diverse mortality patterns using postdrought measurements on surviving trees coupled to retrospective process modelling. The species exhibited a wide range of gas exchange responses, hydraulic strategies, and mortality rates. Multiple proposed indices of mortality mechanisms were inconsistent with the observed mortality patterns across species, including measures of the degree of iso/anisohydry, photosynthesis, carbohydrate depletion, and hydraulic safety margins. Large losses of spring and summer whole-tree conductance (driven by belowground losses of conductance) and shallower rooting depths were associated with species that exhibited greater mortality. Based on this retrospective analysis, we suggest that species more vulnerable to drought were more likely to have succumbed to hydraulic failure belowground.
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Affiliation(s)
- Daniel M Johnson
- College of Natural Resources, University of Idaho, Moscow, ID, 83844, USA
| | - Jean-Christophe Domec
- Bordeaux Sciences Agro, UMR INRA-ISPA 1391, Gradignan, 33195, France
- Nicholas School of the Environment, Duke University, Durham, NC, 27708, USA
| | - Z Carter Berry
- College of Natural Resources, University of Idaho, Moscow, ID, 83844, USA
- Department of Natural Resources and the Environment, University of New Hampshire, Durham, NH, 03824, USA
| | - Amanda M Schwantes
- Nicholas School of the Environment, Duke University, Durham, NC, 27708, USA
| | | | - David R Woodruff
- US Forest Service, Pacific Northwest Research Station, Corvallis, OR, 97331, USA
| | - H Wayne Polley
- Grassland, Soil & Water Research Laboratory USDA-Agricultural Research Service, Temple, TX, 76502, USA
| | - Remí Wortemann
- INRA Nancy, UMR INRA-UL 1137 Ecologie et Ecophysiologie Forestières, Champenoux, 54280, France
| | - Jennifer J Swenson
- Nicholas School of the Environment, Duke University, Durham, NC, 27708, USA
| | - D Scott Mackay
- Department of Geography, State University of New York, Buffalo, NY, 14261, USA
| | - Nate G McDowell
- Pacific Northwest National Laboratory, Richland, WA, 99352, USA
| | - Robert B Jackson
- Department of Earth System Science, Woods Institute for the Environment, and Precourt Institute for Energy, Stanford University, Stanford, CA, 94305, USA
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28
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Chen X, Gao J, Zhao P, McCarthy HR, Zhu L, Ni G, Ouyang L. Tree Species with Photosynthetic Stems Have Greater Nighttime Sap Flux. FRONTIERS IN PLANT SCIENCE 2018; 9:30. [PMID: 29416547 PMCID: PMC5787579 DOI: 10.3389/fpls.2018.00030] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 01/09/2018] [Indexed: 05/14/2023]
Abstract
An increasing body of evidence has shown that nighttime sap flux occurs in most plants, but the physiological implications and regulatory mechanism are poorly known. The significance of corticular photosynthesis has received much attention during the last decade, however, the knowledge of the relationship between corticular photosynthesis and nocturnal stem sap flow is limited at present. In this study, we divided seven tree species into two groups according to different photosynthetic capabilities: trees of species with (Castanopsis hystrix, Michelia macclurei, Eucalyptus citriodora, and Eucalyptus grandis × urophylla) and without (Castanopsis fissa, Schima superba, and Acacia auriculiformis) photosynthetic stems, and the sap flux (Js) and chlorophyll fluorescence parameters for these species were measured. One-way ANOVA analysis showed that the Fv/Fm (Maximum photochemical quantum yield of PSII) and ΦPSII (effective photochemical quantum yield of PSII) values were lower in non-photosynthetic stem species compared to photosynthetic stem species. The linear regression analysis showed that Js,d (daytime sap flux) and Js,n (nighttime sap flux) of non-photosynthetic stem species was 87.7 and 60.9% of the stem photosynthetic species. Furthermore, for a given daytime transpiration water loss, total nighttime sap flux was higher in species with photosynthetic stems (SlopeSMA = 2.680) than in non-photosynthetic stems species (SlopeSMA = 1.943). These results mean that stem corticular photosynthesis has a possible effect on the nighttime water flow, highlighting the important eco-physiological relationship between nighttime sap flux and corticular photosynthesis.
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Affiliation(s)
- Xia Chen
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Jianguo Gao
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
| | - Ping Zhao
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
- Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
| | - Heather R. McCarthy
- Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, United States
| | - Liwei Zhu
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
| | - Guangyan Ni
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
| | - Lei Ouyang
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
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Abstract
The phloem plays a central role in transporting resources and signalling molecules from fully expanded leaves to provide precursors for, and to direct development of, heterotrophic organs located throughout the plant body. We review recent advances in understanding mechanisms regulating loading and unloading of resources into, and from, the phloem network; highlight unresolved questions regarding the physiological significance of the vast array of proteins and RNAs found in phloem saps; and evaluate proposed structure/function relationships considered to account for bulk flow of sap, sustained at high rates and over long distances, through the transport phloem.
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Affiliation(s)
- Johannes Liesche
- Biomass Energy Center for Arid and Semi-arid lands, Northwest A&F University, Yangling, China
- College of Life Science, Northwest A&F University, Yangling , China
| | - John Patrick
- Department of Biological Sciences, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, Australia
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30
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Kleiber A, Duan Q, Jansen K, Verena Junker L, Kammerer B, Rennenberg H, Ensminger I, Gessler A, Kreuzwieser J. Drought effects on root and needle terpenoid content of a coastal and an interior Douglas fir provenance. TREE PHYSIOLOGY 2017; 37:1648-1658. [PMID: 29036462 DOI: 10.1093/treephys/tpx113] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Accepted: 08/15/2017] [Indexed: 05/24/2023]
Abstract
Douglas fir (Pseudotsuga menziesii) is a conifer species that stores large amounts of terpenoids, mainly monoterpenoids in resin ducts of various tissues. The effects of drought on stored leaf terpenoid concentrations in trees are scarcely studied and published data are partially controversial, since reduced, unaffected or elevated terpenoid contents due to drought have been reported. Even less is known on the effect of drought on root terpenoids. In the present work, we investigated the effect of reduced water availability on the terpenoid content in roots and needles of Douglas fir seedlings. Two contrasting Douglas fir provenances were studied: an interior provenance (var. glauca) with assumed higher drought resistance, and a coastal provenance (var. menziesii) with assumed lower drought resistance. We tested the hypothesis that both provenances show specific patterns of stored terpenoids and that the patterns will change in response to drought in both, needles and roots. We further expected stronger changes in the less drought tolerant coastal provenance. For this purpose, we performed an experiment under controlled conditions, in which the trees were exposed to moderate and severe drought stress. According to our expectations, the study revealed clear provenance-specific terpenoid patterns in needles. However, such patterns were not detected in the roots. Drought slightly increased the needle terpenoid contents of the coastal but not of the interior provenance. We also observed increased terpenoid abundance mainly in roots of the moderately stressed coastal provenance. Overall, from the observed provenance-specific reactions with increased terpenoid levels in trees of the coastal origin in response to drought, we conclude on functions of terpenoids for abiotic stress tolerance that might be fulfilled by other, constitutively expressed mechanisms in drought-adapted interior provenances.
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Affiliation(s)
- Anita Kleiber
- Chair of Tree Physiology, Institute of Forest Sciences, Albert-Ludwigs-Universität Freiburg, Georges-Köhler-Allee 53, 79110 Freiburg, Germany
| | - Qiuxiao Duan
- Chair of Tree Physiology, Institute of Forest Sciences, Albert-Ludwigs-Universität Freiburg, Georges-Köhler-Allee 53, 79110 Freiburg, Germany
| | - Kirstin Jansen
- Institute for Landscape Biogeochemistry, Leibniz Centre for Agricultural Landscape Research (ZALF), Eberswalderstr. 84, 15374 Müncheberg, Germany
- Institute of Ecology, Leuphana University of Lüneburg, Scharnhorststrasse 1, 21335 Lüneburg, Germany
| | - Laura Verena Junker
- Department of Biology, Graduate Programs in Cell & Systems Biology and Ecology & Evolutionary Biology, University of Toronto, 3359 Mississauga Road, Mississauga, ON, Canada
- Forest Research Institute of Baden-Württemberg (FVA), Wonnhaldestrasse 4, D-79100 Freiburg i. Brsg., Germany
- Present address: Institute of Bio and Geosciences IBG-2, Plant Sciences, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Bernd Kammerer
- Centre for Biosystems Analysis (ZBSA), Habsburgerstr. 49, Albert-Ludwigs-Universität Freiburg, Germany
| | - Heinz Rennenberg
- Chair of Tree Physiology, Institute of Forest Sciences, Albert-Ludwigs-Universität Freiburg, Georges-Köhler-Allee 53, 79110 Freiburg, Germany
| | - Ingo Ensminger
- Department of Biology, Graduate Programs in Cell & Systems Biology and Ecology & Evolutionary Biology, University of Toronto, 3359 Mississauga Road, Mississauga, ON, Canada
- Forest Research Institute of Baden-Württemberg (FVA), Wonnhaldestrasse 4, D-79100 Freiburg i. Brsg., Germany
| | - Arthur Gessler
- Institute for Landscape Biogeochemistry, Leibniz Centre for Agricultural Landscape Research (ZALF), Eberswalderstr. 84, 15374 Müncheberg, Germany
- Berlin-Brandenburg Institute of Advanced Biodiversity Research (BBIB), 14195 Berlin, Germany
- Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), 8903 Birmensdorf, Switzerland
| | - Jürgen Kreuzwieser
- Chair of Tree Physiology, Institute of Forest Sciences, Albert-Ludwigs-Universität Freiburg, Georges-Köhler-Allee 53, 79110 Freiburg, Germany
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31
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Paljakka T, Jyske T, Lintunen A, Aaltonen H, Nikinmaa E, Hölttä T. Gradients and dynamics of inner bark and needle osmotic potentials in Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies L. Karst). PLANT, CELL & ENVIRONMENT 2017; 40:2160-2173. [PMID: 28671720 DOI: 10.1111/pce.13017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 06/21/2017] [Accepted: 06/22/2017] [Indexed: 06/07/2023]
Abstract
Preconditions of phloem transport in conifers are relatively unknown. We studied the variation of needle and inner bark axial osmotic gradients and xylem water potential in Scots pine and Norway spruce by measuring needle and inner bark osmolality in saplings and mature trees over several periods within a growing season. The needle and inner bark osmolality was strongly related to xylem water potential in all studied trees. Sugar concentrations were measured in Scots pine, and they had similar dynamics to inner bark osmolality. The sucrose quantity remained fairly constant over time and position, whereas the other sugars exhibited a larger change with time and position. A small osmotic gradient existed from branch to stem base under pre-dawn conditions, and the osmotic gradient between upper stem and stem base was close to zero. The turgor in branches was significantly driven by xylem water potential, and the turgor loss point in branches was relatively close to daily minimum needle water potentials typically reported for Scots pine. Our results imply that xylem water potential considerably impacts the turgor pressure gradient driving phloem transport and that gravitation has a relatively large role in phloem transport in the stems of mature Scots pine trees.
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Affiliation(s)
- Teemu Paljakka
- Department of Forest Sciences, University of Helsinki, Helsinki, FI-00014, Finland
| | - Tuula Jyske
- Natural Resources Institute Finland (Luke), FI-02150, Espoo, Finland
| | - Anna Lintunen
- Department of Forest Sciences, University of Helsinki, Helsinki, FI-00014, Finland
| | - Heidi Aaltonen
- Department of Forest Sciences, University of Helsinki, Helsinki, FI-00014, Finland
| | - Eero Nikinmaa
- Department of Forest Sciences, University of Helsinki, Helsinki, FI-00014, Finland
| | - Teemu Hölttä
- Department of Forest Sciences, University of Helsinki, Helsinki, FI-00014, Finland
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32
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Carvalho MR, Turgeon R, Owens T, Niklas KJ. The hydraulic architecture of Ginkgo leaves. AMERICAN JOURNAL OF BOTANY 2017; 104:1285-1298. [PMID: 29885239 DOI: 10.3732/ajb.1700277] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 08/31/2017] [Indexed: 05/24/2023]
Abstract
PREMISE OF THE STUDY The hydraulics of xylem has been widely studied in numerous species and organ types. However, comparatively little is known about how phloem and xylem are hydraulically coupled or about many of the basic structural properties of phloem (such as conducting cell numbers and conductive areas), which nevertheless have direct bearing on understanding phloem loading and unloading. METHODS Using a combination of light, epifluorescence, confocal, and transmission electron microscopy, we quantified the hydraulic architecture of Ginkgo biloba leaf laminae and examined the scaling relationships between phloem and xylem in five fully mature leaves. KEY RESULTS The conductive areas and lengths of sieve cells and tracheids increase basipetally toward the petiole in a manner that is consistent with Münch's pressure flow hypothesis for phloem transport. This trend holds true for individual veins, the sum of conductive areas across all veins at any distance from the petiole, and for individual sieve cells and tracheids. Further, the conductive areas of phloem and xylem are isometrically correlated across the entire vasculature of the leaf lamina. The data for conducting cell areas do not conform with the predictions of the hydraulic models of da Vinci and Murray. CONCLUSIONS The scaling of Ginkgo lamina hydraulics complies with that observed in leaves of other gymnosperms and most angiosperms and is inconsistent with theoretical models that assume that the volume of transported incompressible fluids is conserved.
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Affiliation(s)
- Mónica R Carvalho
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, New York 14853 USA
- Smithsonian Tropical Research Institute, Box 0843-03092, Balboa, Ancon Republic of Panama
| | - Robert Turgeon
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, New York 14853 USA
| | - Thomas Owens
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, New York 14853 USA
| | - Karl J Niklas
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, New York 14853 USA
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33
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Hölttä T, Lintunen A, Chan T, Mäkelä A, Nikinmaa E. A steady-state stomatal model of balanced leaf gas exchange, hydraulics and maximal source-sink flux. TREE PHYSIOLOGY 2017; 37:851-868. [PMID: 28338800 DOI: 10.1093/treephys/tpx011] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2016] [Accepted: 01/23/2017] [Indexed: 05/16/2023]
Abstract
Trees must simultaneously balance their CO2 uptake rate via stomata, photosynthesis, the transport rate of sugars and rate of sugar utilization in sinks while maintaining a favourable water and carbon balance. We demonstrate using a numerical model that it is possible to understand stomatal functioning from the viewpoint of maximizing the simultaneous photosynthetic production, phloem transport and sink sugar utilization rate under the limitation that the transpiration-driven hydrostatic pressure gradient sets for those processes. A key feature in our model is that non-stomatal limitations to photosynthesis increase with decreasing leaf water potential and/or increasing leaf sugar concentration and are thus coupled to stomatal conductance. Maximizing the photosynthetic production rate using a numerical steady-state model leads to stomatal behaviour that is able to reproduce the well-known trends of stomatal behaviour in response to, e.g., light, vapour concentration difference, ambient CO2 concentration, soil water status, sink strength and xylem and phloem hydraulic conductance. We show that our results for stomatal behaviour are very similar to the solutions given by the earlier models of stomatal conductance derived solely from gas exchange considerations. Our modelling results also demonstrate how the 'marginal cost of water' in the unified stomatal conductance model and the optimal stomatal model could be related to plant structural and physiological traits, most importantly, the soil-to-leaf hydraulic conductance and soil moisture.
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Affiliation(s)
- Teemu Hölttä
- Department of Forest Sciences, University of Helsinki, Latokartanonkaari 7, PO Box 27, 00014 Helsinki, Finland
| | - Anna Lintunen
- Department of Forest Sciences, University of Helsinki, Latokartanonkaari 7, PO Box 27, 00014 Helsinki, Finland
| | - Tommy Chan
- Department of Forest Sciences, University of Helsinki, Latokartanonkaari 7, PO Box 27, 00014 Helsinki, Finland
| | - Annikki Mäkelä
- Department of Forest Sciences, University of Helsinki, Latokartanonkaari 7, PO Box 27, 00014 Helsinki, Finland
| | - Eero Nikinmaa
- Department of Forest Sciences, University of Helsinki, Latokartanonkaari 7, PO Box 27, 00014 Helsinki, Finland
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34
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Dietrich D, Pang L, Kobayashi A, Fozard JA, Boudolf V, Bhosale R, Antoni R, Nguyen T, Hiratsuka S, Fujii N, Miyazawa Y, Bae TW, Wells DM, Owen MR, Band LR, Dyson RJ, Jensen OE, King JR, Tracy SR, Sturrock CJ, Mooney SJ, Roberts JA, Bhalerao RP, Dinneny JR, Rodriguez PL, Nagatani A, Hosokawa Y, Baskin TI, Pridmore TP, De Veylder L, Takahashi H, Bennett MJ. Root hydrotropism is controlled via a cortex-specific growth mechanism. NATURE PLANTS 2017; 3:965-972. [PMID: 28481327 DOI: 10.1038/s41477-017-0064-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 10/27/2017] [Indexed: 05/24/2023]
Abstract
Plants can acclimate by using tropisms to link the direction of growth to environmental conditions. Hydrotropism allows roots to forage for water, a process known to depend on abscisic acid (ABA) but whose molecular and cellular basis remains unclear. Here we show that hydrotropism still occurs in roots after laser ablation removed the meristem and root cap. Additionally, targeted expression studies reveal that hydrotropism depends on the ABA signalling kinase SnRK2.2 and the hydrotropism-specific MIZ1, both acting specifically in elongation zone cortical cells. Conversely, hydrotropism, but not gravitropism, is inhibited by preventing differential cell-length increases in the cortex, but not in other cell types. We conclude that root tropic responses to gravity and water are driven by distinct tissue-based mechanisms. In addition, unlike its role in root gravitropism, the elongation zone performs a dual function during a hydrotropic response, both sensing a water potential gradient and subsequently undergoing differential growth.
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Affiliation(s)
- Daniela Dietrich
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Plant &Crop Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
| | - Lei Pang
- Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
| | - Akie Kobayashi
- Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
| | - John A Fozard
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
| | - Véronique Boudolf
- Department of Plant Biotechnology and Bioinformatics, Ghent University, (Technologiepark 927), 9052 Ghent, Belgium
- VIB Center for Plant Systems Biology, (Technologiepark 927), 9052 Ghent, Belgium
| | - Rahul Bhosale
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Plant &Crop Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
- Department of Plant Biotechnology and Bioinformatics, Ghent University, (Technologiepark 927), 9052 Ghent, Belgium
- VIB Center for Plant Systems Biology, (Technologiepark 927), 9052 Ghent, Belgium
| | - Regina Antoni
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
| | - Tuan Nguyen
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- School of Computer Science, University of Nottingham, Nottingham NG8 1BB, UK
| | - Sotaro Hiratsuka
- Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
| | - Nobuharu Fujii
- Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
| | - Yutaka Miyazawa
- Faculty of Science, Yamagata University, Yamagata 990-8560, Japan
| | - Tae-Woong Bae
- Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
| | - Darren M Wells
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Plant &Crop Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
| | - Markus R Owen
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Centre for Mathematical Medicine &Biology, University of Nottingham, Nottingham NG7 2RD, UK
| | - Leah R Band
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Centre for Mathematical Medicine &Biology, University of Nottingham, Nottingham NG7 2RD, UK
| | - Rosemary J Dyson
- School of Mathematics, University of Birmingham, Birmingham B15 2TT, UK
| | - Oliver E Jensen
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- School of Mathematics, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - John R King
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Centre for Mathematical Medicine &Biology, University of Nottingham, Nottingham NG7 2RD, UK
| | - Saoirse R Tracy
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Agricultural and Environmental Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
| | - Craig J Sturrock
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Agricultural and Environmental Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
| | - Sacha J Mooney
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Agricultural and Environmental Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
| | - Jeremy A Roberts
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Plant &Crop Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
| | - Rishikesh P Bhalerao
- Department of Forest Genetics and Plant Physiology, SLU, S-901 83 Umea, Sweden
- College of Science, KSU, Riyadh, Saudi Arabia
| | - José R Dinneny
- Department of Plant Biology, Carnegie Institution for Science, 260 Panama Street, Stanford, California 94305, USA
| | - Pedro L Rodriguez
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Cientificas-Universidad Politecnica de Valencia, ES-46022 Valencia, Spain
| | - Akira Nagatani
- Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Yoichiroh Hosokawa
- Graduate School of Materials Science, Nara Institute of Science &Technology, Ikoma 630-0101, Japan
| | - Tobias I Baskin
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Biology Department, University of Massachusetts, Amherst, Massachusetts 01003-9297, USA
| | - Tony P Pridmore
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- School of Computer Science, University of Nottingham, Nottingham NG8 1BB, UK
| | - Lieven De Veylder
- Department of Plant Biotechnology and Bioinformatics, Ghent University, (Technologiepark 927), 9052 Ghent, Belgium
- VIB Center for Plant Systems Biology, (Technologiepark 927), 9052 Ghent, Belgium
| | - Hideyuki Takahashi
- Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
| | - Malcolm J Bennett
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Plant &Crop Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
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Stanfield RC, Hacke UG, Laur J. Are phloem sieve tubes leaky conduits supported by numerous aquaporins? AMERICAN JOURNAL OF BOTANY 2017; 104:719-732. [PMID: 28526726 DOI: 10.3732/ajb.1600422] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Accepted: 04/20/2017] [Indexed: 05/04/2023]
Abstract
PREMISE OF THE STUDY Aquaporin membrane water channels have been previously identified in the phloem of angiosperms, but currently their cellular characterization is lacking, especially in tree species. Pinpointing the cellular location will help generate new hypotheses of how membrane water exchange facilitates sugar transport in plants. METHODS We studied histological sections of balsam poplar (Populus balsamifera L.) in leaf, petiole, and stem organs. Immuno-labeling techniques were used to characterize the distribution of PIP1 and PIP2 subfamilies of aquaporins along the phloem pathway. Confocal and super resolution microscopy (3D-SIM) was used to identify the localization of aquaporins at the cellular level. KEY RESULTS Sieve tubes of the leaf lamina, petiole, and stem were labeled with antibodies directed at PIP1s and PIP2s. While PIP2s were mostly observed in the plasma membrane, PIP1s showed both an internal membrane and plasma membrane labeling pattern. CONCLUSIONS The specificity and consistency of PIP2 labeling in sieve element plasma membranes points to high water exchange rates between sieve tubes and adjacent cells. The PIP1s may relocate between internal membranes and the plasma membrane to facilitate dynamic changes in membrane permeability of sieve elements in response to changing internal or environmental conditions. Aquaporin-mediated changes in membrane permeability of sieve tubes would also allow for some control of radial exchange of water between xylem and phloem.
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Affiliation(s)
- Ryan C Stanfield
- Department of Renewable Resources, University of Alberta, Edmonton, AB T6G 2E3, Canada; ORCID id: 0000-0002-7507-7550
| | - Uwe G Hacke
- Department of Renewable Resources, University of Alberta, Edmonton, AB T6G 2E3, Canada; ORCID id: 0000-0002-7507-7550
| | - Joan Laur
- Centre de Recherche en Horticulture, Université Laval, Envirotron, Québec, QC G1V0A6, Canada
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Marias DE, Meinzer FC, Still C. Impacts of leaf age and heat stress duration on photosynthetic gas exchange and foliar nonstructural carbohydrates in Coffea arabica. Ecol Evol 2017; 7:1297-1310. [PMID: 28303198 PMCID: PMC5306013 DOI: 10.1002/ece3.2681] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 10/28/2016] [Accepted: 11/27/2016] [Indexed: 01/04/2023] Open
Abstract
Given future climate predictions of increased temperature, and frequency and intensity of heat waves in the tropics, suitable habitat to grow ecologically, economically, and socially valuable Coffea arabica is severely threatened. We investigated how leaf age and heat stress duration impact recovery from heat stress in C. arabica. Treated plants were heated in a growth chamber at 49°C for 45 or 90 min. Physiological recovery was monitored in situ using gas exchange, chlorophyll fluorescence (the ratio of variable to maximum fluorescence, FV/FM), and leaf nonstructural carbohydrate (NSC) on mature and expanding leaves before and 2, 15, 25, and 50 days after treatment. Regardless of leaf age, the 90-min treatment resulted in greater FV/FM reduction 2 days after treatment and slower recovery than the 45-min treatment. In both treatments, photosynthesis of expanding leaves recovered more slowly than in mature leaves. Stomatal conductance (gs) decreased in expanding leaves but did not change in mature leaves. These responses led to reduced intrinsic water-use efficiency with increasing heat stress duration in both age classes. Based on a leaf energy balance model, aftereffects of heat stress would be exacerbated by increases in leaf temperature at low gs under full sunlight where C. arabica is often grown, but also under partial sunlight. Starch and total NSC content of the 45-min group significantly decreased 2 days after treatment and then accumulated 15 and 25 days after treatment coinciding with recovery of photosynthesis and FV/FM. In contrast, sucrose of the 90-min group accumulated at day 2 suggesting that phloem transport was inhibited. Both treatment group responses contrasted with control plant total NSC and starch, which declined with time associated with subsequent flower and fruit production. No treated plants produced flowers or fruits, suggesting that short duration heat stress can lead to crop failure.
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Affiliation(s)
- Danielle E. Marias
- Department of Forest Ecosystems and SocietyOregon State UniversityCorvallisORUSA
| | | | - Christopher Still
- Department of Forest Ecosystems and SocietyOregon State UniversityCorvallisORUSA
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Rodríguez-Calcerrada J, Li M, López R, Cano FJ, Oleksyn J, Atkin OK, Pita P, Aranda I, Gil L. Drought-induced shoot dieback starts with massive root xylem embolism and variable depletion of nonstructural carbohydrates in seedlings of two tree species. THE NEW PHYTOLOGIST 2017; 213:597-610. [PMID: 27575435 DOI: 10.1111/nph.14150] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 07/12/2016] [Indexed: 05/17/2023]
Abstract
Combining hydraulic- and carbon-related measurements helps to understand drought-induced plant mortality. Here, we investigated the role that plant respiration (R) plays in determining carbon budgets under drought. We measured the hydraulic conductivity of stems and roots, and gas exchange and nonstructural carbohydrate (NSC) concentrations of leaves, stems and roots of seedlings of two resprouting species exposed to drought or well-watered conditions: Ulmus minor (riparian tree) and Quercus ilex (dryland tree). With increasing water stress (occurring more rapidly in larger U. minor), declines in leaf, stem and root R were less pronounced than that in leaf net photosynthetic CO2 uptake (Pn ). Daytime whole-plant carbon gain was negative below -4 and -6 MPa midday xylem water potential in U. minor and Q. ilex, respectively. Relative to controls, seedlings exhibiting shoot dieback suffered c. 80% loss of hydraulic conductivity in both species, and reductions in NSC concentrations in U. minor. Higher drought-induced depletion of NSC reserves in U. minor was related to higher plant R, faster stomatal closure, and premature leaf-shedding. Differences in drought resistance relied on the ability to maintain hydraulic conductivity during drought, rather than tolerating conductivity loss. Root hydraulic failure elicited shoot dieback and precluded resprouting without root NSC reserves being apparently limiting for R.
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Affiliation(s)
- Jesús Rodríguez-Calcerrada
- Forest History, Physiology and Genetics Research Group, School of Forestry Engineering, Technical University of Madrid, Madrid, 28040, Spain
| | - Meng Li
- Forest History, Physiology and Genetics Research Group, School of Forestry Engineering, Technical University of Madrid, Madrid, 28040, Spain
| | - Rosana López
- Forest History, Physiology and Genetics Research Group, School of Forestry Engineering, Technical University of Madrid, Madrid, 28040, Spain
- Hawkesbury Institute for the Environment, UWS, Science Road, Richmond, 2753, NSW, Australia
| | - Francisco Javier Cano
- Forest History, Physiology and Genetics Research Group, School of Forestry Engineering, Technical University of Madrid, Madrid, 28040, Spain
- Hawkesbury Institute for the Environment, UWS, Science Road, Richmond, 2753, NSW, Australia
| | - Jacek Oleksyn
- Institute of Dendrology, Polish Academy of Sciences, Kórnik, 62-035, Poland
| | - Owen K Atkin
- ARC Centre of Excellence in Plant Energy Biology, Division of Plant Sciences, Research School of Biology, The Australian National University, Building 134, Canberra, ACT, 2601, Australia
| | - Pilar Pita
- Forest History, Physiology and Genetics Research Group, School of Forestry Engineering, Technical University of Madrid, Madrid, 28040, Spain
| | - Ismael Aranda
- Department of Forest Ecology and Genetics, Forest Research Centre, INIA, Avda. A Coruña km 7.5, 28040, Madrid, Spain
| | - Luis Gil
- Forest History, Physiology and Genetics Research Group, School of Forestry Engineering, Technical University of Madrid, Madrid, 28040, Spain
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Sack L, Ball MC, Brodersen C, Davis SD, Des Marais DL, Donovan LA, Givnish TJ, Hacke UG, Huxman T, Jansen S, Jacobsen AL, Johnson DM, Koch GW, Maurel C, McCulloh KA, McDowell NG, McElrone A, Meinzer FC, Melcher PJ, North G, Pellegrini M, Pockman WT, Pratt RB, Sala A, Santiago LS, Savage JA, Scoffoni C, Sevanto S, Sperry J, Tyerman SD, Way D, Holbrook NM. Plant hydraulics as a central hub integrating plant and ecosystem function: meeting report for 'Emerging Frontiers in Plant Hydraulics' (Washington, DC, May 2015). PLANT, CELL & ENVIRONMENT 2016; 39:2085-94. [PMID: 27037757 DOI: 10.1111/pce.12732] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Accepted: 03/06/2016] [Indexed: 05/25/2023]
Abstract
Water plays a central role in plant biology and the efficiency of water transport throughout the plant affects both photosynthetic rate and growth, an influence that scales up deterministically to the productivity of terrestrial ecosystems. Moreover, hydraulic traits mediate the ways in which plants interact with their abiotic and biotic environment. At landscape to global scale, plant hydraulic traits are important in describing the function of ecological communities and ecosystems. Plant hydraulics is increasingly recognized as a central hub within a network by which plant biology is connected to palaeobiology, agronomy, climatology, forestry, community and ecosystem ecology and earth-system science. Such grand challenges as anticipating and mitigating the impacts of climate change, and improving the security and sustainability of our food supply rely on our fundamental knowledge of how water behaves in the cells, tissues, organs, bodies and diverse communities of plants. A workshop, 'Emerging Frontiers in Plant Hydraulics' supported by the National Science Foundation, was held in Washington DC, 2015 to promote open discussion of new ideas, controversies regarding measurements and analyses, and especially, the potential for expansion of up-scaled and down-scaled inter-disciplinary research, and the strengthening of connections between plant hydraulic research, allied fields and global modelling efforts.
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Affiliation(s)
- Lawren Sack
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA
| | - Marilyn C Ball
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory, 0200, Australia
| | - Craig Brodersen
- School of Forestry & Environmental Studies, Yale University, 195 Prospect Street, New Haven, CT, 06511, USA
| | - Stephen D Davis
- Natural Science Division, Pepperdine University, Malibu, CA, 90263, USA
| | - David L Des Marais
- Arnold Arboretum, Harvard University, Cambridge, MA, 02131, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Boston, MA, 02138, USA
| | - Lisa A Donovan
- Department of Plant Biology, University of Georgia, Athens, GA, 30602, USA
| | - Thomas J Givnish
- Department of Botany, University of Wisconsin Madison, Madison, WI, 53706, USA
| | - Uwe G Hacke
- Department of Renewable Resources, University of Alberta, Edmonton, Alberta, T6G 2E3, Canada
| | - Travis Huxman
- Ecology and Evolutionary Biology & Center for Environmental Biology, University of California, Irvine, CA, 92697, USA
| | - Steven Jansen
- Ulm University, Institute of Systematic Botany and Ecology, Albert-Einstein-Allee 11, Ulm, 89081, Germany
| | - Anna L Jacobsen
- Department of Biology, California State University, Bakersfield, CA, 93311, USA
| | - Daniel M Johnson
- Department of Forest, Rangeland and Fire Sciences, University of Idaho, Moscow, ID, 83844, USA
| | - George W Koch
- Center for Ecosystem Science and Society, and Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, 86011, USA
| | - Christophe Maurel
- Biochimie et Physiologie Moléculaire des Plantes, UMR 5004, INRA-CNRS-Sup Agro-Université de Montpellier, 2 Place Viala, Montpellier, F-34060, France
| | | | - Nate G McDowell
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Andrew McElrone
- Department of Viticulture and Enology, University of California, Davis, CA, 95616, USA
- USDA-Agricultural Research Service, Davis, CA, 95616, USA
| | - Frederick C Meinzer
- Pacific Northwest Research Station, USDA Forest Service, Corvallis, OR, 97331, USA
| | - Peter J Melcher
- Department of Biology, Ithaca College, Ithaca, NY, 14850, USA
| | - Gretchen North
- Department of Biology, Occidental College, Los Angeles, CA, 90041, USA
| | - Matteo Pellegrini
- Department of Molecular, Cell, and Developmental Biology, University of California Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA
| | - William T Pockman
- Department of Biology, MSC03 2020, University of New Mexico, Albuquerque, NM, 87131, USA
| | - R Brandon Pratt
- Department of Biology, California State University, Bakersfield, CA, 93311, USA
| | - Anna Sala
- Division of Biological Sciences, University of Montana, Missoula, MT, 59812, USA
| | - Louis S Santiago
- Botany and Plant Sciences, University of California, Riverside, CA, 92521, USA
| | - Jessica A Savage
- Arnold Arboretum, Harvard University, Cambridge, MA, 02131, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Boston, MA, 02138, USA
| | - Christine Scoffoni
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA
| | - Sanna Sevanto
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - John Sperry
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT, 84112, USA
| | - Stephen D Tyerman
- ARC Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, Waite Research Precinct, The University of Adelaide, PMB 1, Glen Osmond, South Australia, 5064, Australia
| | - Danielle Way
- Department of Biology, Western University, 1151 Richmond Street, London, Ontario, N6A 5B7, Canada
| | - N Michele Holbrook
- Department of Organismic and Evolutionary Biology, Harvard University, Boston, MA, 02138, USA
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Kwang-Hua CR. Effects of activation energy and activation volume on the temperature-dependent viscosity of water. Phys Rev E 2016; 94:022424. [PMID: 27627349 DOI: 10.1103/physreve.94.022424] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Indexed: 06/06/2023]
Abstract
Water transport in a leaf is vulnerable to viscosity-induced changes. Recent research has suggested that these changes may be partially due to variation at the molecular scale, e.g., regulations via aquaporins, that induce reductions in leaf hydraulic conductance. What are the quantitative as well as qualitative changes in temperature-dependent viscosity due to the role of aquaporins in tuning activation energy and activation volume? Using the transition-state approach as well as the boundary perturbation method, we investigate temperature-dependent viscosity tuned by activation energy and activation volume. To validate our approach, we compare our numerical results with previous temperature-dependent viscosity measurements. The rather good fit between our calculations and measurements confirms our present approach. We have obtained critical parameters for the temperature-dependent (shear) viscosity of water that might be relevant to the increasing and reducing of leaf hydraulic conductance. These parameters are sensitive to temperature, activation energy, and activation volume. Once the activation energy increases, the (shear) viscosity of water increases. Our results also show that as the activation volume increases (say, 10^{-23}m^{3}), the (shear) viscosity of water decreases significantly and the latter induces the enhancing of leaf hydraulic conductance. Within the room-temperature regime, a small increase in the activation energy will increase the water viscosity or reduce the leaf hydraulic conductance. Our approach and results can be applied to diverse plant or leaf attributes.
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Affiliation(s)
- Chu Rainer Kwang-Hua
- Transfer Centre, 4/F, No. 16, Lane 21, Kwang-Hui Road, Taipei, Taiwan 116, Republic of China and Distribution Centre, Golmud Mansion, 33, Road Yingbin, Golmud 816000, China
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40
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Savage JA, Clearwater MJ, Haines DF, Klein T, Mencuccini M, Sevanto S, Turgeon R, Zhang C. Allocation, stress tolerance and carbon transport in plants: how does phloem physiology affect plant ecology? PLANT, CELL & ENVIRONMENT 2016; 39:709-25. [PMID: 26147312 DOI: 10.1111/pce.12602] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 05/30/2015] [Accepted: 06/19/2015] [Indexed: 05/02/2023]
Abstract
Despite the crucial role of carbon transport in whole plant physiology and its impact on plant-environment interactions and ecosystem function, relatively little research has tried to examine how phloem physiology impacts plant ecology. In this review, we highlight several areas of active research where inquiry into phloem physiology has increased our understanding of whole plant function and ecological processes. We consider how xylem-phloem interactions impact plant drought tolerance and reproduction, how phloem transport influences carbon allocation in trees and carbon cycling in ecosystems and how phloem function mediates plant relations with insects, pests, microbes and symbiotes. We argue that in spite of challenges that exist in studying phloem physiology, it is critical that we consider the role of this dynamic vascular system when examining the relationship between plants and their biotic and abiotic environment.
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Affiliation(s)
- Jessica A Savage
- Arnold Arboretum of Harvard University, 1300 Centre Street, Boston, MA, 02131, USA
| | | | - Dustin F Haines
- Department of Environmental Conservation, University of Massachusetts, 160 Holdsworth Way, Amherst, MA, 01003, USA
| | - Tamir Klein
- Institute of Botany, University of Basel, Schoenbeinstrasse 6, 4056, Basel, Switzerland
| | - Maurizio Mencuccini
- School of GeoSciences, University of Edinburgh, Crew Building, West Mains Road, EH9 3JN, Edinburgh, UK
- ICREA at CREAF, Campus de UAB, Cerdanyola del Valles, Barcelona, 08023, Spain
| | - Sanna Sevanto
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Robert Turgeon
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, NY, 14853, USA
| | - Cankui Zhang
- Department of Agronomy, Purdue University, West Lafayette, IN, 47907, USA
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Epron D, Cabral OMR, Laclau JP, Dannoura M, Packer AP, Plain C, Battie-Laclau P, Moreira MZ, Trivelin PCO, Bouillet JP, Gérant D, Nouvellon Y. In situ 13CO2 pulse labelling of field-grown eucalypt trees revealed the effects of potassium nutrition and throughfall exclusion on phloem transport of photosynthetic carbon. TREE PHYSIOLOGY 2016; 36:6-21. [PMID: 26423335 DOI: 10.1093/treephys/tpv090] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 08/10/2015] [Indexed: 05/15/2023]
Abstract
Potassium (K) is an important limiting factor of tree growth, but little is known of the effects of K supply on the long-distance transport of photosynthetic carbon (C) in the phloem and of the interaction between K fertilization and drought. We pulse-labelled 2-year-old Eucalyptus grandis L. trees grown in a field trial combining K fertilization (+K and -K) and throughfall exclusion (+W and -W), and we estimated the velocity of C transfer by comparing time lags between the uptake of (13)CO2 and its recovery in trunk CO2 efflux recorded at different heights. We also analysed the dynamics of the labelled photosynthates recovered in the foliage and in the phloem sap (inner bark extract). The mean residence time of labelled C in the foliage was short (21-31 h). The time series of (13)C in excess in the foliage was affected by the level of fertilization, whereas the effect of throughfall exclusion was not significant. The velocity of C transfer in the trunk (0.20-0.82 m h(-1)) was twice as high in +K trees than in -K trees, with no significant effect of throughfall exclusion except for one +K -W tree labelled in the middle of the drought season that was exposed to a more pronounced water stress (midday leaf water potential of -2.2 MPa). Our results suggest that besides reductions in photosynthetic C supply and in C demand by sink organs, the lower velocity under K deficiency is due to a lower cross-sectional area of the sieve tubes, whereas an increase in phloem sap viscosity is more likely limiting phloem transport under drought. In all treatments, 10 times less (13)C was recovered in inner bark extracts at the bottom of the trunk when compared with the base of the crown, suggesting that a large part of the labelled assimilates has been exported out of the phloem and replaced by unlabelled C. This supports the 'leakage-retrieval mechanism' that may play a role in maintaining the pressure gradient between source and sink organs required to sustain high velocity of phloem transport in tall trees.
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Affiliation(s)
- Daniel Epron
- UMR 1137, Ecologie et Ecophysiologie Forestières, Faculté des Sciences, Université de Lorraine, F-54500 Vandoeuvre-les-Nancy, France INRA, UMR 1137, Ecologie et Ecophysiologie Forestières, Centre de Nancy, F-54280 Champenoux, France CIRAD, UMR Eco&sols, Ecologie Fonctionnelle & Biogéochimie des Sols & Agro-écosystèmes, F-34060 Montpellier, France
| | | | - Jean-Paul Laclau
- CIRAD, UMR Eco&sols, Ecologie Fonctionnelle & Biogéochimie des Sols & Agro-écosystèmes, F-34060 Montpellier, France Universidade Estadual de São Paulo, Botucatu, CEP 18610-300 São Paulo, Brazil Departamento de Ciências Florestais, ESALQ, Universidade de São Paulo, ESALQ, CEP 13418-900 Piracicaba, São Paulo, Brazil
| | - Masako Dannoura
- Laboratory of Forest Utilization, Department of Forest and Biomaterial Science, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
| | - Ana Paula Packer
- Embrapa Meio Ambiente, CEP 13820-000, Jaguariúna, São Paulo, Brazil
| | - Caroline Plain
- UMR 1137, Ecologie et Ecophysiologie Forestières, Faculté des Sciences, Université de Lorraine, F-54500 Vandoeuvre-les-Nancy, France INRA, UMR 1137, Ecologie et Ecophysiologie Forestières, Centre de Nancy, F-54280 Champenoux, France
| | - Patricia Battie-Laclau
- Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, CEP 13400-970 Piracicaba, São Paulo, Brazil
| | - Marcelo Zacharias Moreira
- Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, CEP 13400-970 Piracicaba, São Paulo, Brazil
| | - Paulo Cesar Ocheuze Trivelin
- Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, CEP 13400-970 Piracicaba, São Paulo, Brazil
| | - Jean-Pierre Bouillet
- CIRAD, UMR Eco&sols, Ecologie Fonctionnelle & Biogéochimie des Sols & Agro-écosystèmes, F-34060 Montpellier, France Departamento de Ciências Florestais, ESALQ, Universidade de São Paulo, ESALQ, CEP 13418-900 Piracicaba, São Paulo, Brazil
| | - Dominique Gérant
- UMR 1137, Ecologie et Ecophysiologie Forestières, Faculté des Sciences, Université de Lorraine, F-54500 Vandoeuvre-les-Nancy, France INRA, UMR 1137, Ecologie et Ecophysiologie Forestières, Centre de Nancy, F-54280 Champenoux, France
| | - Yann Nouvellon
- CIRAD, UMR Eco&sols, Ecologie Fonctionnelle & Biogéochimie des Sols & Agro-écosystèmes, F-34060 Montpellier, France Departamento de Ciências Atmosféricas, IAG, Universidade de São Paulo, ESALQ, CEP 05508-900 São Paulo, Brazil
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Vandegehuchte MW, Bloemen J, Vergeynst LL, Steppe K. Woody tissue photosynthesis in trees: salve on the wounds of drought? THE NEW PHYTOLOGIST 2015; 208:998-1002. [PMID: 26226885 DOI: 10.1111/nph.13599] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 07/08/2015] [Indexed: 05/24/2023]
Affiliation(s)
- Maurits W Vandegehuchte
- Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000, Ghent, Belgium
| | - Jasper Bloemen
- Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000, Ghent, Belgium
- Institute of Ecology, Research Group Ecophysiology and Ecosystem Processes, University of Innsbruck, Sternwartestraβe 15, 6020, Innsbruck, Austria
| | - Lidewei L Vergeynst
- Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000, Ghent, Belgium
| | - Kathy Steppe
- Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000, Ghent, Belgium
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Scartazza A, Moscatello S, Matteucci G, Battistelli A, Brugnoli E. Combining stable isotope and carbohydrate analyses in phloem sap and fine roots to study seasonal changes of source-sink relationships in a Mediterranean beech forest. TREE PHYSIOLOGY 2015; 35:829-39. [PMID: 26093372 DOI: 10.1093/treephys/tpv048] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 05/09/2015] [Indexed: 05/05/2023]
Abstract
Carbon isotope composition (δ(13)C) and carbohydrate content of phloem sap and fine roots were measured in a Mediterranean beech (Fagus sylvatica L.) forest throughout the growing season to study seasonal changes of source-sink relationships. Seasonal variations of δ(13)C and content of phloem sap sugars, collected during the daylight period, reflected the changes in soil and plant water status. The correlation between δ(13)C and content of phloem sap sugars, collected from plants belonging to different social classes, was significantly positive only during the driest month of July. In this month, δ(13)C of phloem sap sugars was inversely related to the increment of trunk radial growth and positively related to δ(13)C of fine roots. We conclude that the relationship between δ(13)C and the amount of phloem sap sugars is affected by a combination of causes, such as sink strength, tree social class, changes in phloem anatomy and transport capacity, and phloem loading of sugars to restore sieve tube turgor following the reduced plant water potential under drought conditions. However, δ(13)C and sugar composition of fine roots suggested that phloem transport of leaf sucrose to this belowground component was not impaired by mild drought and that sucrose was in a large part allocated towards fine roots in July, depending on tree social class. Hence, fine roots could represent a functional carbon sink during the dry seasonal periods, when transport and use of assimilates in other sink tissues are reduced. These results indicate a strict link between above- and belowground processes and highlight a rapid response of this Mediterranean forest to changes in environmental drivers to regulate source-sink relationships and carbon sink capacity.
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Affiliation(s)
- Andrea Scartazza
- Istituto di Biologia Agroambientale e Forestale (IBAF), Consiglio Nazionale delle Ricerche (CNR), Via Salaria km 29,300, 00016 Monterotondo Scalo (RM), Italy Istituto di Biologia Agroambientale e Forestale (IBAF), Consiglio Nazionale delle Ricerche (CNR), Viale G. Marconi 2, 05010 Porano (TR), Italy
| | - Stefano Moscatello
- Istituto di Biologia Agroambientale e Forestale (IBAF), Consiglio Nazionale delle Ricerche (CNR), Viale G. Marconi 2, 05010 Porano (TR), Italy
| | - Giorgio Matteucci
- Istituto di Biologia Agroambientale e Forestale (IBAF), Consiglio Nazionale delle Ricerche (CNR), Via Salaria km 29,300, 00016 Monterotondo Scalo (RM), Italy Istituto per i Sistemi Agricoli e Forestali del Mediterraneo (ISAFoM), Consiglio Nazionale delle Ricerche (CNR), Via Cavour 4/6, 87036 Rende (CS), Italy
| | - Alberto Battistelli
- Istituto di Biologia Agroambientale e Forestale (IBAF), Consiglio Nazionale delle Ricerche (CNR), Viale G. Marconi 2, 05010 Porano (TR), Italy
| | - Enrico Brugnoli
- Istituto di Biologia Agroambientale e Forestale (IBAF), Consiglio Nazionale delle Ricerche (CNR), Viale G. Marconi 2, 05010 Porano (TR), Italy Present address: Dipartimento Scienze del Sistema Terra e Tecnologie per l'Ambiente, Consiglio Nazionale delle Ricerche (CNR), Piazzale Aldo Moro 7, 00185 Roma (RM), Italy
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Reinhardt K, Germino MJ, Kueppers LM, Domec JC, Mitton J. Linking carbon and water relations to drought-induced mortality in Pinus flexilis seedlings. TREE PHYSIOLOGY 2015; 35:771-82. [PMID: 26116925 DOI: 10.1093/treephys/tpv045] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 04/24/2015] [Indexed: 05/24/2023]
Abstract
Survival of tree seedlings at high elevations has been shown to be limited by thermal constraints on carbon balance, but it is unknown if carbon relations also limit seedling survival at lower elevations, where water relations may be more important. We measured and modeled carbon fluxes and water relations in first-year Pinus flexilis seedlings in garden plots just beyond the warm edge of their natural range, and compared these with dry-mass gain and survival across two summers. We hypothesized that mortality in these seedlings would be associated with declines in water relations, more so than with carbon-balance limitations. Rather than gradual declines in survivorship across growing seasons, we observed sharp, large-scale mortality episodes that occurred once volumetric soil-moisture content dropped below 10%. By this point, seedling water potentials had decreased below -5 MPa, seedling hydraulic conductivity had decreased by 90% and seedling hydraulic resistance had increased by >900%. Additionally, non-structural carbohydrates accumulated in aboveground tissues at the end of both summers, suggesting impairments in phloem-transport from needles to roots. This resulted in low carbohydrate concentrations in roots, which likely impaired root growth and water uptake at the time of critically low soil moisture. While photosynthesis and respiration on a leaf area basis remained high until critical hydraulic thresholds were exceeded, modeled seedling gross primary productivity declined steadily throughout the summers. At the time of mortality, modeled productivity was insufficient to support seedling biomass-gain rates, metabolism and secondary costs. Thus the large-scale mortality events that we observed near the end of each summer were most directly linked with acute, episodic declines in plant hydraulic function that were linked with important changes in whole-seedling carbon relations.
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Affiliation(s)
- Keith Reinhardt
- Department of Biological Sciences, Idaho State University, Pocatello, ID 83209-8007, USA
| | - Matthew J Germino
- United States Geological Survey, Forest and Rangeland Ecosystem Science Center, Boise, ID 83706, USA
| | - Lara M Kueppers
- Sierra Nevada Research Institute, University of California, Merced, CA 95343, USA
| | - Jean-Christophe Domec
- Bordeaux Sciences Agro, INRA ISPA UMR 1391, 33175 Gradignan, France Nicholas School of the Environment, Duke University, Durham, NC 27708, USA
| | - Jeffry Mitton
- Department of Ecology and Evolutionary Biology, University of Colorado-Boulder, Boulder, CO 80309, USA
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Pfautsch S, Hölttä T, Mencuccini M. Hydraulic functioning of tree stems--fusing ray anatomy, radial transfer and capacitance. TREE PHYSIOLOGY 2015; 35:706-22. [PMID: 26163488 DOI: 10.1093/treephys/tpv058] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 05/20/2015] [Indexed: 05/11/2023]
Abstract
Not long ago, textbooks on plant physiology divulged the view that phloem and xylem are separate transport systems with exclusive functions. Phloem was flowing downwards providing roots with carbohydrates. Xylem transported water upwards from roots to leaves. This simplified view has changed forever. Today we have a much-refined understanding of the complex transport mechanisms, regulatory functions and surprisingly ingenuous solutions trees have evolved to distribute carbohydrates and water internally to fuel growth and help mediate biotic and abiotic stresses. This review focuses on functional links between tissues of the inner bark region (i.e., more than just phloem) and the xylem, facilitated by radially aligned and interconnected parenchyma cells, called rays. Rays are usually found along the entire vertical axis of tree stems, mediating a number of transport processes. We use a top-down approach to unveil the role of rays in these processes. Due to the central role of rays in facilitating the coupling of inner bark and xylem we dedicate the first section to ray anatomy, pathways and control mechanisms involved in radial transport. In the second section, basic concepts and models for radial movement through rays are introduced and their impacts on water and carbon fluxes at the whole-tree level are discussed. This section is followed by a closer look at the capacitive function of composite tissues in stems where gradual changes in water potential generate a diurnal 'pulse'. We explain how this pulse can be measured and interpreted, and where the limitations of such analyses are. Towards the end of this review, we include a brief description of the role of radial transport during limited availability of water. By elucidating the strong hydraulic link between inner bark and xylem, the traditional view of two separate transport systems dissolves and the idea of one interconnected, yet highly segregated transport network for carbohydrates and water arises.
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Affiliation(s)
- Sebastian Pfautsch
- Hawkesbury Institute for the Environment, University of Western Sydney, Locked Bag 1797, Penrith 2751, NSW, Australia
| | - Teemu Hölttä
- Department of Forest Sciences, University of Helsinki, PO Box 27, FIN-00014, Finland
| | - Maurizio Mencuccini
- School of Geo-Science, University of Edinburgh, West Mains Road, Edinburgh EH9 3JN, UK ICREA at CREAF, Campus de UAB, Cerdanyola del Valles 08023, Barcelona, Spain
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Asao S, Ryan MG. Carbohydrate regulation of photosynthesis and respiration from branch girdling in four species of wet tropical rain forest trees. TREE PHYSIOLOGY 2015; 35:608-620. [PMID: 25870320 DOI: 10.1093/treephys/tpv025] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 02/26/2015] [Indexed: 06/04/2023]
Abstract
How trees sense source-sink carbon balance remains unclear. One potential mechanism is a feedback from non-structural carbohydrates regulating photosynthesis and removing excess as waste respiration when the balance of photosynthesis against growth and metabolic activity changes. We tested this carbohydrate regulation of photosynthesis and respiration using branch girdling in four tree species in a wet tropical rainforest in Costa Rica. Because girdling severs phloem to stop carbohydrate export while leaving xylem intact to allow photosynthesis, we expected carbohydrates to accumulate in leaves to simulate a carbon imbalance. We varied girdling intensity by removing phloem in increments of one-quarter of the circumference (zero, one--quarter, half, three-quarters, full) and surrounded a target branch with fully girdled ones to create a gradient in leaf carbohydrate content. Light saturated photosynthesis rate was measured in situ, and foliar respiration rate and leaf carbohydrate content were measured after destructive harvest at the end of the treatment. Girdling intensity created no consistent or strong responses in leaf carbohydrates. Glucose and fructose slightly increased in all species by 3.4% per one-quarter girdle, total carbon content and leaf mass per area increased only in one species by 5.4 and 5.5% per one-quarter girdle, and starch did not change. Only full girdling lowered photosynthesis in three of four species by 59-69%, but the decrease in photosynthesis was unrelated to the increase in glucose and fructose content. Girdling did not affect respiration. The results suggest that leaf carbohydrate content remains relatively constant under carbon imbalance, and any changes are unlikely to regulate photosynthesis or respiration. Because girdling also stops the export of hormones and reactive oxygen species, girdling may induce physiological changes unrelated to carbohydrate accumulation and may not be an effective method to study carbohydrate feedback in leaves. In three species, removal of three-quarters of phloem area did not cause leaf carbohydrates to accumulate nor did it change photosynthesis or respiration, suggesting that phloem transport is flexible and transport rate per unit phloem can rapidly increase under an increase in carbohydrate supply relative to phloem area. Leaf carbohydrate content thus may be decoupled from whole plant carbon balance by phloem transport in some species, and carbohydrate regulation of photosynthesis and respiration may not be as common in trees as previous girdling studies suggest. Further studies in carbohydrate regulation should avoid using girdling as girdling can decrease photosynthesis through unintended means without the tested mechanisms of accumulating leaf carbohydrates.
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Affiliation(s)
- Shinichi Asao
- Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523-1401, USA Natural Resources Ecology Laboratory, Colorado State University, Fort Collins, CO 80523-1499, USA
| | - Michael G Ryan
- Natural Resources Ecology Laboratory, Colorado State University, Fort Collins, CO 80523-1499, USA Emeritus, USDA Forest Service, Rocky Mountain Research Station, 240 West Prospect Street, Fort Collins, CO 80526, USA
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Woodruff DR, Meinzer FC, Marias DE, Sevanto S, Jenkins MW, McDowell NG. Linking nonstructural carbohydrate dynamics to gas exchange and leaf hydraulic behavior in Pinus edulis and Juniperus monosperma. THE NEW PHYTOLOGIST 2015; 206:411-421. [PMID: 25412472 DOI: 10.1111/nph.13170] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 10/20/2014] [Indexed: 05/03/2023]
Abstract
Leaf hydraulics, gas exchange and carbon storage in Pinus edulis and Juniperus monosperma, two tree species on opposite ends of the isohydry-anisohydry spectrum, were analyzed to examine relationships between hydraulic function and carbohydrate dynamics. Leaf hydraulic vulnerability, leaf water potential (Ψl ), leaf hydraulic conductance (Kleaf ), photosynthesis (A), stomatal conductance (gs) and nonstructural carbohydrate (NSC) content were analyzed throughout the growing season. Leaf hydraulic vulnerability was significantly lower in the relatively anisohydric J. monosperma than in the more isohydric P. edulis. In P. edulis, Ψl dropped and stayed below 50% loss of leaf hydraulic conductance (P₅₀) early in the day during May, August and around midday in September, leading to sustained reductions in Kleaf . In J. monosperma, Ψl dropped below P₅₀ only during August, resulting in the maintenance of Kleaf during much of the growing season. Mean A and gs during September were significantly lower in P. edulis than in J. monosperma. Foliar total NSC was two to three times greater in J. monosperma than in P. edulis in June, August and September. Consistently lower levels of total NSC in P. edulis suggest that its isohydric strategy pushes it towards the exhaustion of carbon reserves during much of the growing season.
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Affiliation(s)
- David R Woodruff
- USDA Forest Service, PNW Research Station, 3200 SW Jefferson Way, Corvallis, OR, 97331, USA
| | - Frederick C Meinzer
- USDA Forest Service, PNW Research Station, 3200 SW Jefferson Way, Corvallis, OR, 97331, USA
| | - Danielle E Marias
- College for Forestry, Oregon State University, Corvallis, OR, 97331, USA
| | - Sanna Sevanto
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Michael W Jenkins
- Department of Environmental Studies, University of California, Santa Cruz, CA, 95064, USA
| | - Nate G McDowell
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
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48
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Jyske T, Hölttä T. Comparison of phloem and xylem hydraulic architecture in Picea abies stems. THE NEW PHYTOLOGIST 2015; 205:102-15. [PMID: 25124270 DOI: 10.1111/nph.12973] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 07/06/2014] [Indexed: 05/23/2023]
Abstract
The hydraulic properties of xylem and phloem differ but the magnitude and functional consequences of the differences are not well understood. Phloem and xylem functional areas, hydraulic conduit diameters and conduit frequency along the stems of Picea abies trees were measured and expressed as allometric functions of stem diameter and distance from stem apex. Conductivities of phloem and xylem were estimated from these scaling relations. Compared with xylem, phloem conduits were smaller and occupied a slightly larger fraction of conducting tissue area. Ten times more xylem than phloem was annually produced along the stem. Scaling of the conduit diameters and cross-sectional areas with stem diameter were very similar in phloem and xylem. Phloem and xylem conduits scaled also similarly with distance from stem apex; widening downwards from the tree top, and reaching a plateau near the base of the living crown. Phloem conductivity was estimated to scale similarly to the conductivity of the outermost xylem ring, with the ratio of phloem to xylem conductivity being c. 2%. However, xylem conductivity was estimated to increase more than phloem conductivity with increasing tree dimensions as a result of accumulation of xylem sapwood. Phloem partly compensated for its smaller conducting area and narrower conduits by having a slightly higher conduit frequency.
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Affiliation(s)
- Tuula Jyske
- Vantaa Research Unit, Finnish Forest Research Institute, PO Box 18, FI-01301, Vantaa, Finland
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49
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Affiliation(s)
- Michael G Ryan
- Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO 89523, USA
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50
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Fanwoua J, Bairam E, Delaire M, Buck-Sorlin G. The role of branch architecture in assimilate production and partitioning: the example of apple (Malus domestica). FRONTIERS IN PLANT SCIENCE 2014; 5:338. [PMID: 25071813 PMCID: PMC4089354 DOI: 10.3389/fpls.2014.00338] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 06/25/2014] [Indexed: 05/21/2023]
Abstract
Understanding the role of branch architecture in carbon production and allocation is essential to gain more insight into the complex process of assimilate partitioning in fruit trees. This mini review reports on the current knowledge of the role of branch architecture in carbohydrate production and partitioning in apple. The first-order carrier branch of apple illustrates the complexity of branch structure emerging from bud activity events and encountered in many fruit trees. Branch architecture influences carbon production by determining leaf exposure to light and by affecting leaf internal characteristics related to leaf photosynthetic capacity. The dynamics of assimilate partitioning between branch organs depends on the stage of development of sources and sinks. The sink strength of various branch organs and their relative positioning on the branch also affect partitioning. Vascular connections between branch organs determine major pathways for branch assimilate transport. We propose directions for employing a modeling approach to further elucidate the role of branch architecture on assimilate partitioning.
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Affiliation(s)
- Julienne Fanwoua
- *Correspondence: Julienne Fanwoua, UMR 1345 Institut de Recherche en Horticulture et Semences, AGROCAMPUS OUEST-Centre d’Angers, Institut National d’Horticulture et de Paysage 2 Rue André le Notre, 49045 Angers Cedex 01, France e-mail:
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