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Martínez-Vilalta J, Garcia-Forner N. Water potential regulation, stomatal behaviour and hydraulic transport under drought: deconstructing the iso/anisohydric concept. PLANT, CELL & ENVIRONMENT 2017; 40:962-976. [PMID: 27739594 DOI: 10.1111/pce.12846] [Citation(s) in RCA: 186] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Revised: 10/03/2016] [Accepted: 10/04/2016] [Indexed: 05/02/2023]
Abstract
In this review, we address the relationship between stomatal behaviour, water potential regulation and hydraulic transport in plants, focusing on the implications for the iso/anisohydric classification of plant drought responses at seasonal timescales. We first revise the history of the isohydric concept and its possible definitions. Then, we use published data to answer two main questions: (1) is greater stomatal control in response to decreasing water availability associated with a tighter regulation of leaf water potential (ΨL ) across species? and (2) is there an association between tighter ΨL regulation (~isohydric behaviour) and lower leaf conductance over time during a drought event? These two questions are addressed at two levels: across species growing in different sites and comparing only species coexisting at a given site. Our analyses show that, across species, a tight regulation of ΨL is not necessarily associated with greater stomatal control or with more constrained assimilation during drought. Therefore, iso/anisohydry defined in terms of ΨL regulation cannot be used as an indicator of a specific mechanism of drought-induced mortality or as a proxy for overall plant vulnerability to drought.
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Affiliation(s)
- Jordi Martínez-Vilalta
- CREAF, Cerdanyola del Vallès, Barcelona, E-08193, Spain
- Universitat Autònoma Barcelona, Cerdanyola del Vallès, Barcelona, E-08193, Spain
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Nardini A, Savi T, Trifilò P, Lo Gullo MA. Drought Stress and the Recovery from Xylem Embolism in Woody Plants. PROGRESS IN BOTANY VOL. 79 2017. [DOI: 10.1007/124_2017_11] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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53
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Hura T, Tyrka M, Hura K, Ostrowska A, Dziurka K. QTLs for cell wall-bound phenolics in relation to the photosynthetic apparatus activity and leaf water status under drought stress at different growth stages of triticale. Mol Genet Genomics 2016; 292:415-433. [DOI: 10.1007/s00438-016-1276-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 11/28/2016] [Indexed: 01/16/2023]
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Blessing CH, Barthel M, Gentsch L, Buchmann N. Strong Coupling of Shoot Assimilation and Soil Respiration during Drought and Recovery Periods in Beech As Indicated by Natural Abundance δ 13C Measurements. FRONTIERS IN PLANT SCIENCE 2016; 7:1710. [PMID: 27909442 PMCID: PMC5112276 DOI: 10.3389/fpls.2016.01710] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Accepted: 10/31/2016] [Indexed: 05/27/2023]
Abstract
Drought down-regulates above- and belowground carbon fluxes, however, the resilience of trees to drought will also depend on the speed and magnitude of recovery of these above- and belowground fluxes after re-wetting. Carbon isotope composition of above- and belowground carbon fluxes at natural abundance provides a methodological approach to study the coupling between photosynthesis and soil respiration (SR) under conditions (such as drought) that influence photosynthetic carbon isotope discrimination. In turn, the direct supply of root respiration with recent photoassimilates will impact on the carbon isotope composition of soil-respired CO2. We independently measured shoot and soil CO2 fluxes of beech saplings (Fagus sylvatica L.) and their respective δ13C continuously with laser spectroscopy at natural abundance. We quantified the speed of recovery of drought stressed trees after re-watering and traced photosynthetic carbon isotope signal in the carbon isotope composition of soil-respired CO2. Stomatal conductance responded strongly to the moderate drought (-65%), induced by reduced soil moisture content as well as increased vapor pressure deficit. Simultaneously, carbon isotope discrimination decreased by 8‰, which in turn caused a significant increase in δ13C of recent metabolites (1.5-2.5‰) and in δ13C of SR (1-1.5‰). Generally, shoot and soil CO2 fluxes and their δ13C were in alignment during drought and subsequent stress release, clearly demonstrating a permanent dependence of root respiration on recently fixed photoassimilates, rather than on older reserves. After re-watering, the drought signal persisted longer in δ13C of the water soluble fraction that integrates multiple metabolites (soluble sugars, amino acids, organic acids) than in the neutral fraction which represents most recently assimilated sugars or in the δ13C of SR. Nevertheless, full recovery of all aboveground physiological variables was reached within 4 days - and within 7 days for SR - indicating high resilience of (young) beech against moderate drought.
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Affiliation(s)
- Carola H. Blessing
- Centre for Carbon Water and Food, University of Sydney, Brownlow HillNSW, Australia
- Institute of Agricultural Sciences, ETH ZürichZürich, Switzerland
| | - Matti Barthel
- Institute of Agricultural Sciences, ETH ZürichZürich, Switzerland
| | - Lydia Gentsch
- Chair of Bioclimatology, Georg-August University of GöttingenGöttingen, Germany
| | - Nina Buchmann
- Institute of Agricultural Sciences, ETH ZürichZürich, Switzerland
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Petit G, Savi T, Consolini M, Anfodillo T, Nardini A. Interplay of growth rate and xylem plasticity for optimal coordination of carbon and hydraulic economies in Fraxinus ornus trees. TREE PHYSIOLOGY 2016; 36:1310-1319. [PMID: 27587483 DOI: 10.1093/treephys/tpw069] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Revised: 06/17/2016] [Accepted: 07/02/2016] [Indexed: 05/22/2023]
Abstract
Efficient leaf water supply is fundamental for assimilation processes and tree growth. Renovating the architecture of the xylem transport system requires an increasing carbon investment while growing taller, and any deficiency of carbon availability may result in increasing hydraulic constraints to water flow. Therefore, plants need to coordinate carbon assimilation and biomass allocation to guarantee an efficient and safe long-distance transport system. We tested the hypothesis that reduced branch elongation rates together with carbon-saving adjustments of xylem anatomy hydraulically compensate for the reduction in biomass allocation to xylem. We measured leaf biomass, hydraulic and anatomical properties of wood segments along the main axis of branches in 10 slow growing (SG) and 10 fast growing (FG) Fraxinus ornus L. trees. Branches of SG trees had five times slower branch elongation rate (7 vs 35 cm year-1), and produced a higher leaf biomass (P < 0.0001) and thinner xylem rings with fewer but larger vessels (P < 0.0001). On the contrary, we found no differences between SG and FG trees in terms of leaf-specific conductivity (P > 0.05) and xylem safety (Ψ50 ≈ -3.2 MPa). Slower elongation rate coupled with thinner annual rings and larger vessels allows the reduction of carbon costs associated with growth, while maintaining similar leaf-specific conductivity and xylem safety.
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Affiliation(s)
- Giai Petit
- Dipartimento Territorio e Sistemi Agro-Forestali, Università degli Studi di Padova, Viale dell'Università 16, I-35020 Legnaro (PD), Italy
| | - Tadeja Savi
- Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, 34127 Trieste, Italy
| | - Martina Consolini
- Dipartimento Territorio e Sistemi Agro-Forestali, Università degli Studi di Padova, Viale dell'Università 16, I-35020 Legnaro (PD), Italy
| | - Tommaso Anfodillo
- Dipartimento Territorio e Sistemi Agro-Forestali, Università degli Studi di Padova, Viale dell'Università 16, I-35020 Legnaro (PD), Italy
| | - Andrea Nardini
- Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, 34127 Trieste, Italy
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Duarte AG, Katata G, Hoshika Y, Hossain M, Kreuzwieser J, Arneth A, Ruehr NK. Immediate and potential long-term effects of consecutive heat waves on the photosynthetic performance and water balance in Douglas-fir. JOURNAL OF PLANT PHYSIOLOGY 2016; 205:57-66. [PMID: 27614786 DOI: 10.1016/j.jplph.2016.08.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Revised: 08/19/2016] [Accepted: 08/22/2016] [Indexed: 05/16/2023]
Abstract
The frequency and intensity of climatic extremes, such as heat waves, are predicted to increase globally, with severe implications for terrestrial carbon and water cycling. Temperatures may rise above critical thresholds that allow trees to function optimally, with unknown long-term consequences for forest ecosystems. In this context, we investigated how photosynthetic traits and the water balance in Douglas-fir are affected by exposure to three heat waves with temperatures about 12°C above ambient. Photosynthetic carboxylation efficiency (Vcmax) was mostly unaffected, but electron transport (Jmax) and photosynthetic rates under saturating light (Asat) were strongly influenced by the heat waves, with lagging limitations on photosynthesis still being observed six weeks after the last heat wave. We also observed lingering heat-induced inhibitions on transpiration, minimum stomatal conductance, and night-time stomatal conductance (gs-night). Results from the stomatal models used to calculate minimum stomatal conductance were similar to gs-night and indicated changes in leaf morphology, e.g. stomatal occlusions and alterations in epicuticular wax. Our results show Douglas-fir's ability to restrict water loss following heat stress, but at the price of reduced photosynthetic performance. Such limitations indicate potential long-term restrictions that heat waves can impose on tree development and functioning under extreme climatic conditions.
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Affiliation(s)
- André G Duarte
- Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research-Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany; The University of Western Ontario, 1151 Richmond St., London, ON, N6A 3K7, Canada.
| | - Genki Katata
- Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research-Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany; Japan Atomic Energy Agency, Ibaraki, Japan
| | - Yasutomo Hoshika
- Institute of Sustainable Plant Protection, National Research Council of Italy, Turin, Italy
| | - Mohitul Hossain
- Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research-Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany; The University of Western Australia, Perth, Australia
| | | | - Almut Arneth
- Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research-Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany
| | - Nadine K Ruehr
- Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research-Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany
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57
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Li Y, Chen W, Chen J, Shi H. Contrasting hydraulic strategies in Salix psammophila and Caragana korshinskii in the southern Mu Us Desert, China. Ecol Res 2016. [DOI: 10.1007/s11284-016-1396-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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58
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Zhang Z, Zhao P, McCarthy HR, Ouyang L, Niu J, Zhu L, Ni G, Huang Y. Hydraulic Balance of a Eucalyptus urophylla Plantation in Response to Periodic Drought in Low Subtropical China. FRONTIERS IN PLANT SCIENCE 2016; 7:1346. [PMID: 27725821 PMCID: PMC5036442 DOI: 10.3389/fpls.2016.01346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/05/2016] [Accepted: 08/22/2016] [Indexed: 06/06/2023]
Abstract
A clear understanding of hydraulic regulation in cultivated plants is crucial for addressing challenges to forest water cycling due to climate changes in low subtropical China. Experiments were conducted to determine the hydrologic balance of a Eucalyptus urophylla plantation in response to periodic drought. Trees displayed lower stomatal conductance (GS) and leaf water potentials (ΨL) during the dry periods. A decrease of 22.4% was found for the maximum reference GS (GS at D = 1 kPa; GSref-max). Accordingly, specific hydraulic conductivity (ks) decreased by 45.3 - 65.6% from the wet to the dry season, depending on the tree size. Fairly stable leaf stomatal conductance (gs) with decreasing ΨL (ΨL < -1.6 MPa) contributed to the high water-use efficiency (WUE) of this Eucalyptus species. Additionally, the lower stomatal sensitivity (-m = 0.53) in the dry season might also be responsible for the high WUE, since we found an anisohydric behavior that was associated with photosynthetically active radiation (Q0). Larger trees were found to use water more efficiently than small trees, due to the higher sensitivity of ks to decreasing ΨL. This was also verified by the decreasing leaf carbon isotope discrimination (Δ13C) with increasing tree diameter. However, further studies are needed to determine the universality of these results for other Eucalyptus species in this region.
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Affiliation(s)
- Zhenzhen Zhang
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Institute of Botany (CAS)Guangzhou, China
- College of Life Sciences, University of Chinese Academy of SciencesBeijing, China
| | - Ping Zhao
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Institute of Botany (CAS)Guangzhou, China
- Guangdong Provincial Key Laboratory of Applied Botany, South China Institute of Botany (CAS)Guangzhou, China
| | - Heather R. McCarthy
- Department of Microbiology and Plant Biology, University of Oklahoma, NormanOK, USA
| | - Lei Ouyang
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Institute of Botany (CAS)Guangzhou, China
| | - Junfeng Niu
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Institute of Botany (CAS)Guangzhou, China
| | - Liwei Zhu
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Institute of Botany (CAS)Guangzhou, China
| | - Guangyan Ni
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Institute of Botany (CAS)Guangzhou, China
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Savi T, Casolo V, Luglio J, Bertuzzi S, Trifilo' P, Lo Gullo MA, Nardini A. Species-specific reversal of stem xylem embolism after a prolonged drought correlates to endpoint concentration of soluble sugars. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2016; 106:198-207. [PMID: 27174138 DOI: 10.1016/j.plaphy.2016.04.051] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 04/28/2016] [Accepted: 04/29/2016] [Indexed: 05/23/2023]
Abstract
Recent reports on tree mortality associated with anomalous drought and heat have raised interest into processes underlying tree resistance/resilience to water stress. Hydraulic failure and carbon starvation have been proposed as main causes of tree decline, with recent theories treating water and carbon metabolism as interconnected processes. We subjected young plants of two native (Quercus pubescens [Qp] and Prunus mahaleb [Pm]) and two invasive (Robinia pseudoacacia [Rp] and Ailanthus altissima [Aa]) woody angiosperms to a prolonged drought leading to stomatal closure and xylem embolism, to induce carbon starvation and hydraulic failure. At the end of the treatment, plants were measured for embolism rates and NSC content, and re-irrigated to monitor recovery of xylem hydraulics. Data highlight different hydraulic strategies in native vs invasive species under water stress, and provide physiological explanations for species-specific impacts of recent severe droughts. Drought-sensitive species (Qp and Rp) suffered high embolism rates and were unable to completely refill xylem conduits upon restoration of water availability. Species that better survived recent droughts were able to limit embolism build-up (Pm) or efficiently restored hydraulic functionality after irrigation (Aa). Species-specific capacity to reverse xylem embolism correlated to stem-level concentration of soluble carbohydrates, but not to starch content.
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Affiliation(s)
- Tadeja Savi
- Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, 34127 Trieste, Italy
| | - Valentino Casolo
- Dipartimento di Scienze AgroAlimentari, Ambientali e Animali, Università di Udine, Viale delle Scienze 91, 33100 Udine, Italy
| | - Jessica Luglio
- Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, 34127 Trieste, Italy
| | - Stefano Bertuzzi
- Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, 34127 Trieste, Italy
| | - Patrizia Trifilo'
- Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali, Università di Messina, Viale Ferdinando Stagno d'Alcontres 31, 98166 Messina, Italy
| | - Maria A Lo Gullo
- Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali, Università di Messina, Viale Ferdinando Stagno d'Alcontres 31, 98166 Messina, Italy
| | - Andrea Nardini
- Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, 34127 Trieste, Italy.
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60
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Olsovska K, Kovar M, Brestic M, Zivcak M, Slamka P, Shao HB. Genotypically Identifying Wheat Mesophyll Conductance Regulation under Progressive Drought Stress. FRONTIERS IN PLANT SCIENCE 2016; 7:1111. [PMID: 27551283 PMCID: PMC4976106 DOI: 10.3389/fpls.2016.01111] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 07/12/2016] [Indexed: 05/19/2023]
Abstract
Photosynthesis limitation by CO2 flow constraints from sub-stomatal cavities to carboxylation sites in chloroplasts under drought stress conditions is, at least in some plant species or crops not fully understood, yet. Leaf mesophyll conductance for CO2 (gm) may considerably affect both photosynthesis and water use efficiency (WUE) in plants under drought conditions. The aim of our study was to detect the responses of gm in leaves of four winter wheat (Triticum aestivum L.) genotypes from different origins under long-term progressive drought. Based on the measurement of gas-exchange parameters the variability of genotypic responses was analyzed at stomatal (stomata closure) and non-stomatal (diffusional and biochemical) limits of net CO2 assimilation rate (AN). In general, progressive drought caused an increasing leaf diffusion resistance against CO2 flow leading to the decrease of AN, gm and stomatal conductance (gs), respectively. Reduction of gm also led to inhibition of carboxylation efficiency (Vcmax). On the basis of achieved results a strong positive relationship between gm and gs was found out indicating a co-regulation and mutual independence of the relationship under the drought conditions. In severely stressed plants, the stomatal limitation of the CO2 assimilation rate was progressively increased, but to a less extent in comparison to gm, while a non-stomatal limitation became more dominant due to the prolonged drought. Mesophyll conductance (gm) seems to be a suitable mechanism and parameter for selection of improved diffusional properties and photosynthetic carbon assimilation in C3 plants, thus explaining their better photosynthetic performance at a whole plant level during periods of drought.
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Affiliation(s)
- Katarina Olsovska
- Jiangsu Key Laboratory for Bioresources of Saline Soils, Provincial Key Laboratory of Agrobiology, Institute of Agro-biotechnology, Jiangsu Academy of Agricultural SciencesNanjing, China
- Department of Plant Physiology, Faculty of Agrobiology and Food Resources, Slovak University of Agriculture in NitraNitra, Slovakia
| | - Marek Kovar
- Department of Plant Physiology, Faculty of Agrobiology and Food Resources, Slovak University of Agriculture in NitraNitra, Slovakia
| | - Marian Brestic
- Jiangsu Key Laboratory for Bioresources of Saline Soils, Provincial Key Laboratory of Agrobiology, Institute of Agro-biotechnology, Jiangsu Academy of Agricultural SciencesNanjing, China
- Department of Plant Physiology, Faculty of Agrobiology and Food Resources, Slovak University of Agriculture in NitraNitra, Slovakia
| | - Marek Zivcak
- Department of Plant Physiology, Faculty of Agrobiology and Food Resources, Slovak University of Agriculture in NitraNitra, Slovakia
| | - Pavol Slamka
- Department of Agrochemistry and Plant Nutrition, Faculty of Agrobiology and Food Resources, Slovak University of Agriculture in NitraNitra, Slovakia
| | - Hong Bo Shao
- Jiangsu Key Laboratory for Bioresources of Saline Soils, Provincial Key Laboratory of Agrobiology, Institute of Agro-biotechnology, Jiangsu Academy of Agricultural SciencesNanjing, China
- Yantai Institute of Coastal Zone Research, Chinese Academy of SciencesYantai, China
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61
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West AG, Nel JA, Bond WJ, Midgley JJ. Experimental evidence for heat plume-induced cavitation and xylem deformation as a mechanism of rapid post-fire tree mortality. THE NEW PHYTOLOGIST 2016; 211:828-38. [PMID: 27152877 PMCID: PMC5084795 DOI: 10.1111/nph.13979] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 03/18/2016] [Indexed: 05/17/2023]
Abstract
Recent work suggests that hydraulic mechanisms, rather than cambium necrosis, may account for rapid post-fire tree mortality. We experimentally tested for xylem cavitation, as a result of exposure to high-vapour-deficit (D) heat plumes, and permanent xylem deformation, as a result of thermal softening of lignin, in two tree species differing in fire tolerance. We measured percentage loss of conductance (PLC) in distal branches that had been exposed to high-D heat plumes or immersed in hot water baths (high temperature, but not D). Results were compared with predictions from a parameterized hydraulic model. Physical damage to the xylem was examined microscopically. Both species suffered c. 80% PLC when exposed to a 100°C plume. However, at 70°C, the fire-sensitive Kiggelaria africana suffered lower PLC (49%) than the fire-resistant Eucalytpus cladocalyx (80%). Model simulations suggested that differences in PLC between species were a result of greater hydraulic segmentation in E. cladocalyx. Kiggelaria africana suffered considerable PLC (59%), as a result of heat-induced xylem deformation, in the water bath treatments, but E. cladocalyx did not. We suggest that a suite of 'pyrohydraulic' traits, including hydraulic segmentation and heat sensitivity of the xylem, may help to explain why some tree species experience rapid post-fire mortality after low-intensity fires and others do not.
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Affiliation(s)
- Adam G. West
- Department of Biological SciencesUniversity of Cape TownRondebosch7700South Africa
| | - Jacques A. Nel
- Department of Biological SciencesUniversity of Cape TownRondebosch7700South Africa
| | - William J. Bond
- Department of Biological SciencesUniversity of Cape TownRondebosch7700South Africa
| | - Jeremy J. Midgley
- Department of Biological SciencesUniversity of Cape TownRondebosch7700South Africa
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Khan MN, Komatsu S. Proteomic analysis of soybean root including hypocotyl during recovery from drought stress. J Proteomics 2016; 144:39-50. [PMID: 27292084 DOI: 10.1016/j.jprot.2016.06.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 06/02/2016] [Accepted: 06/06/2016] [Indexed: 01/24/2023]
Abstract
UNLABELLED Soybean is a nutritionally important crop that exhibits reductions in growth and yield under drought stress. To investigate soybean responses during post-drought recovery, a gel-free proteomic technique was used. Two-day-old soybeans were treated with drought stress for 4days and recovered for 4days. Root including hypocotyl was collected during the drought treatment and recovery stage. Seedling growth was suppressed by drought stress, but recovered following stress removal. The malondialdehyde content increased under drought stress, but decreased during the recovery stage. A total of 792 and 888 proteins were identified from the control and recovering seedlings, respectively. The identified proteins were related to functional categories of stress, hormone metabolism, cell wall, secondary metabolism, and fermentation. Cluster analysis indicated that abundances of peroxidase and aldehyde dehydrogenase were highly changed in the seedlings during the post-drought recovery. The activity of peroxidase decreased under drought conditions, but increased during recovery. In contrast, the activity of aldehyde dehydrogenase was increased in response to drought stress, but decreased during the recovery stage. These results suggest that peroxidase and aldehyde dehydrogenase play key roles in post-drought recovery in soybean by scavenging toxic reactive oxygen species and reducing the load of harmful aldehydes. BIOLOGICAL SIGNIFICANCE Post-drought recovery response mechanisms in soybean root including hypocotyl were analyzed using gel-free proteomic technique. A total of 643 common proteins between control and drought-stressed soybeans changed significantly in abundance over time. The proteins that changed during post-drought recovery were assigned to protein, stress, hormone metabolism, secondary metabolism, cell wall, redox, and glycolysis categories. The analysis revealed that peroxidase and aldehyde dehydrogenase were increased in protein abundance under drought stress. The enzyme activity of peroxidase decreased under drought but increased during recovery. The activity of aldehyde dehydrogenase was increased under drought stress but decreased during recovery stage. Peroxidase and aldehyde dehydrogenase reduce the toxic reactive oxygen species and aldehydes from the plant, respectively, and help to recover from drought stress. The study provides information about post-drought recovery mechanism in soybean.
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Affiliation(s)
- Mudassar Nawaz Khan
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba 305-8572, Japan; National Institute of Crop Science, National Agriculture and Food Research Organization, Tsukuba 305-8518, Japan
| | - Setsuko Komatsu
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba 305-8572, Japan; National Institute of Crop Science, National Agriculture and Food Research Organization, Tsukuba 305-8518, Japan.
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63
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Rodríguez-Gamir J, Primo-Millo E, Forner-Giner MÁ. An Integrated View of Whole-Tree Hydraulic Architecture. Does Stomatal or Hydraulic Conductance Determine Whole Tree Transpiration? PLoS One 2016; 11:e0155246. [PMID: 27223695 PMCID: PMC4880183 DOI: 10.1371/journal.pone.0155246] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 04/26/2016] [Indexed: 11/19/2022] Open
Abstract
Hydraulic conductance exerts a strong influence on many aspects of plant physiology, namely: transpiration, CO2 assimilation, growth, productivity or stress response. However we lack full understanding of the contribution of root or shoot water transport capacity to the total water balance, something which is difficult to study in trees. Here we tested the hypothesis that whole plant hydraulic conductance modulates plant transpiration using two different seedlings of citrus rootstocks, Poncirus trifoliata (L.) Raf. and Cleopatra mandarin (Citrus reshni Hort ex Tan.). The two genotypes presented important differences in their root or shoot hydraulic conductance contribution to whole plant hydraulic conductance but, even so, water balance proved highly dependent on whole plant conductance. Further, we propose there is a possible equilibrium between root and shoot hydraulic conductance, similar to that between shoot and root biomass production, which could be related with xylem anatomy.
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Affiliation(s)
- Juan Rodríguez-Gamir
- Department of Citriculture and Vegetal Production, Valencian Institute of Agrarias Research, Moncada, Valencia, Spain
| | - Eduardo Primo-Millo
- Department of Citriculture and Vegetal Production, Valencian Institute of Agrarias Research, Moncada, Valencia, Spain
| | - María Ángeles Forner-Giner
- Department of Citriculture and Vegetal Production, Valencian Institute of Agrarias Research, Moncada, Valencia, Spain
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Xue W, Nay-Htoon B, Lindner S, Dubbert M, Otieno D, Ko J, Werner C, Tenhunen J. Soil water availability and capacity of nitrogen accumulation influence variations of intrinsic water use efficiency in rice. JOURNAL OF PLANT PHYSIOLOGY 2016; 193:26-36. [PMID: 26938938 DOI: 10.1016/j.jplph.2016.02.003] [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: 11/08/2015] [Revised: 02/03/2016] [Accepted: 02/03/2016] [Indexed: 05/28/2023]
Abstract
Leaf intrinsic water use efficiency (WUEi) coupling maximum assimilation rate (Amax) and transpirable water lost via stomatal conductance (gsc) has been gaining increasing concern in sustainable crop production. Factors that influence leaf Amax and WUEi in rice (Oryza sativa L. cv Unkang) at flooding and rainfed conditions were evaluated. Positive correlations for leaf nitrogen content (Nm) and maximum carboxylation rate (Vcmax), for nitrogen allocation in Rubisco enzymes and mesophyll conductance (gm) were evident independent of cropping cultures. Rainfed rice exhibited enriched canopy leaf average Nm resulting in higher Amax, partially supporting improved leaf WUEi. Maximum WUEi (up to 0.14 μmol mmol(-1)) recorded in rainfed rice under drought conditions resulted from increasing gm/gsc ratio while at cost of significant decline in Amax due to hydraulically constrained gsc. Amax sensitivity related to gsc which was regulated by plant hydraulic conductance. WUEi was tightly correlated to Vcmax/gsc and gm/gsc ratios across the paddy and rainfed not to light environment, morphological and physiological traits, highlighting enhance capacity of Nm accumulation in rainfed rice with gsc at moderately high level similar to paddy rice facilitate optimization in Amax and WUEi while, is challenged by drought-vulnerable plant hydraulic conductance.
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Affiliation(s)
- Wei Xue
- Department of Plant Ecology, BayCEER, University of Bayreuth, 95440, Bayreuth, Germany; State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, 830011 Urumqi, China.
| | - Bhone Nay-Htoon
- Department of Agroecosystem Research, BayCEER, University of Bayreuth, 95440, Bayreuth, Germany
| | - Steve Lindner
- Department of Plant Ecology, BayCEER, University of Bayreuth, 95440, Bayreuth, Germany
| | - Maren Dubbert
- Department of Agroecosystem Research, BayCEER, University of Bayreuth, 95440, Bayreuth, Germany; Department of Ecosystem Physiology, University of Freiburg, 79085 Freiburg, Germany
| | - Dennis Otieno
- Department of Plant Ecology, BayCEER, University of Bayreuth, 95440, Bayreuth, Germany
| | - Jonghan Ko
- Department of Applied Plant Science, Chonnam National University, 500757 Gwangju, South Korea
| | - Christiane Werner
- Department of Agroecosystem Research, BayCEER, University of Bayreuth, 95440, Bayreuth, Germany; Department of Ecosystem Physiology, University of Freiburg, 79085 Freiburg, Germany
| | - John Tenhunen
- Department of Plant Ecology, BayCEER, University of Bayreuth, 95440, Bayreuth, Germany
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O’Keefe K, Nippert JB, Swemmer AM. Savanna Tree Seedlings are Physiologically Tolerant to Nighttime Freeze Events. FRONTIERS IN PLANT SCIENCE 2016; 7:46. [PMID: 26870065 PMCID: PMC4735699 DOI: 10.3389/fpls.2016.00046] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Accepted: 01/12/2016] [Indexed: 05/26/2023]
Abstract
Freeze events can be important disturbances in savanna ecosystems, yet the interactive effect of freezing with other environmental drivers on plant functioning is unknown. Here, we investigated physiological responses of South African tree seedlings to interactions of water availability and freezing temperatures. We grew widely distributed South African tree species (Colophospermum mopane, Combretum apiculatum, Acacia nigrescens, and Cassia abbreviata) under well-watered and water-limited conditions and exposed individuals to nighttime freeze events. Of the four species studied here, C. mopane was the most tolerant of lower water availability. However, all species were similarly tolerant to nighttime freezing and recovered within one week following the last freezing event. We also show that water limitation somewhat increased freezing tolerance in one of the species (C. mopane). Therefore, water limitation, but not freezing temperatures, may restrict the distribution of these species, although the interactions of these stressors may have species-specific impacts on plant physiology. Ultimately, we show that unique physiologies can exist among dominant species within communities and that combined stresses may play a currently unidentified role in driving the function of certain species within southern Africa.
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Li S, Feifel M, Karimi Z, Schuldt B, Choat B, Jansen S. Leaf gas exchange performance and the lethal water potential of five European species during drought. TREE PHYSIOLOGY 2016; 36:179-92. [PMID: 26614785 DOI: 10.1093/treephys/tpv117] [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: 04/30/2015] [Accepted: 10/05/2015] [Indexed: 05/04/2023]
Abstract
Establishing physiological thresholds to drought-induced mortality in a range of plant species is crucial in understanding how plants respond to severe drought. Here, five common European tree species were selected (Acer campestre L., Acer pseudoplatanus L., Carpinus betulus L., Corylus avellana L. and Fraxinus excelsior L.) to study their hydraulic thresholds to mortality. Photosynthetic parameters during desiccation and the recovery of leaf gas exchange after rewatering were measured. Stem vulnerability curves and leaf pressure-volume curves were investigated to understand the hydraulic coordination of stem and leaf tissue traits. Stem and root samples from well-watered and severely drought-stressed plants of two species were observed using transmission electron microscopy to visualize mortality of cambial cells. The lethal water potential (ψlethal) correlated with stem P99 (i.e., the xylem water potential at 99% loss of hydraulic conductivity, PLC). However, several plants that were stressed beyond the water potential at 100% PLC showed complete recovery during the next spring, which suggests that the ψlethal values were underestimated. Moreover, we observed a 1 : 1 relationship between the xylem water potential at the onset of embolism and stomatal closure, confirming hydraulic coordination between leaf and stem tissues. Finally, ultrastructural changes in the cytoplasm of cambium tissue and mortality of cambial cells are proposed to provide an alternative approach to investigate the point of no return associated with plant death.
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Affiliation(s)
- Shan Li
- Institute for Systematic Botany and Ecology, Ulm University, D-89081 Ulm, Germany
| | - Marion Feifel
- Institute for Systematic Botany and Ecology, Ulm University, D-89081 Ulm, Germany
| | - Zohreh Karimi
- Institute for Systematic Botany and Ecology, Ulm University, D-89081 Ulm, Germany Department of Biology, Faculty of Science, Golestan University, 36154 Gorgan, Iran
| | - Bernhard Schuldt
- Plant Ecology, Albrecht von Haller Institute for Plant Sciences, University of Göttingen, D-37077 Göttingen, Germany
| | - Brendan Choat
- University of Western Sydney, Hawkesbury Institute for the Environment, Richmond, NSW 2753, Australia
| | - Steven Jansen
- Institute for Systematic Botany and Ecology, Ulm University, D-89081 Ulm, Germany
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67
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Nolf M, Creek D, Duursma R, Holtum J, Mayr S, Choat B. Stem and leaf hydraulic properties are finely coordinated in three tropical rain forest tree species. PLANT, CELL & ENVIRONMENT 2015; 38:2652-61. [PMID: 26032606 DOI: 10.1111/pce.12581] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Revised: 05/15/2015] [Accepted: 05/18/2015] [Indexed: 05/05/2023]
Abstract
Coordination of stem and leaf hydraulic traits allows terrestrial plants to maintain safe water status under limited water supply. Tropical rain forests, one of the world's most productive biomes, are vulnerable to drought and potentially threatened by increased aridity due to global climate change. However, the relationship of stem and leaf traits within the plant hydraulic continuum remains understudied, particularly in tropical species. We studied within-plant hydraulic coordination between stems and leaves in three tropical lowland rain forest tree species by analyses of hydraulic vulnerability [hydraulic methods and ultrasonic emission (UE) analysis], pressure-volume relations and in situ pre-dawn and midday water potentials (Ψ). We found finely coordinated stem and leaf hydraulic features, with a strategy of sacrificing leaves in favour of stems. Fifty percent of hydraulic conductivity (P50 ) was lost at -2.1 to -3.1 MPa in stems and at -1.7 to -2.2 MPa in leaves. UE analysis corresponded to hydraulic measurements. Safety margins (leaf P50 - stem P50 ) were very narrow at -0.4 to -1.4 MPa. Pressure-volume analysis and in situ Ψ indicated safe water status in stems but risk of hydraulic failure in leaves. Our study shows that stem and leaf hydraulics were finely tuned to avoid embolism formation in the xylem.
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Affiliation(s)
- Markus Nolf
- Institute of Botany, University of Innsbruck, 6020, Innsbruck, Austria
- Hawkesbury Institute for the Environment, University of Western Sydney, Richmond, New South Wales, 2753, Australia
| | - Danielle Creek
- Hawkesbury Institute for the Environment, University of Western Sydney, Richmond, New South Wales, 2753, Australia
| | - Remko Duursma
- Hawkesbury Institute for the Environment, University of Western Sydney, Richmond, New South Wales, 2753, Australia
| | - Joseph Holtum
- School of Marine and Tropical Biology, James Cook University, Townsville, Queensland, 4811, Australia
| | - Stefan Mayr
- Institute of Botany, University of Innsbruck, 6020, Innsbruck, Austria
| | - Brendan Choat
- Hawkesbury Institute for the Environment, University of Western Sydney, Richmond, New South Wales, 2753, Australia
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68
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Knipfer T, Eustis A, Brodersen C, Walker AM, McElrone AJ. Grapevine species from varied native habitats exhibit differences in embolism formation/repair associated with leaf gas exchange and root pressure. PLANT, CELL & ENVIRONMENT 2015; 38:1503-13. [PMID: 25495925 DOI: 10.1111/pce.12497] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2014] [Revised: 11/06/2014] [Accepted: 11/06/2014] [Indexed: 05/23/2023]
Abstract
Drought induces xylem embolism formation, but grapevines can refill non-functional vessels to restore transport capacity. It is unknown whether vulnerability to embolism formation and ability to repair differ among grapevine species. We analysed in vivo embolism formation and repair using x-ray computed microtomography in three wild grapevine species from varied native habitats (Vitis riparia, V. arizonica, V. champinii) and related responses to measurements of leaf gas exchange and root pressure. Vulnerability to embolism formation was greatest in V. riparia, intermediate in V. arizonica and lowest in V. champinii. After re-watering, embolism repair was rapid and pronounced in V. riparia and V. arizonica, but limited or negligible in V. champinii even after numerous days. Similarly, root pressure measured after re-watering was positively correlated with drought stress severity for V. riparia and V. arizonica (species exhibiting embolism repair) but not for V. champinii. Drought-induced reductions in transpiration were greatest for V. riparia and least in V. champinii. Recovery of transpiration after re-watering was delayed for all species, but was greatest for V. champinii and most rapid in V. arizonica. These species exhibit varied responses to drought stress that involve maintenance/recovery of xylem transport capacity coordinated with root pressure and gas exchange responses.
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Affiliation(s)
- Thorsten Knipfer
- Department of Viticulture & Enology, University of California, Davis, CA, 95616, USA
| | - Ashley Eustis
- Department of Viticulture & Enology, University of California, Davis, CA, 95616, USA
| | - Craig Brodersen
- School of Forestry and Environmental Studies, Yale University, New Haven, CT, 06511, USA
| | - Andrew M Walker
- Department of Viticulture & Enology, University of California, Davis, CA, 95616, USA
| | - Andrew J McElrone
- Department of Viticulture & Enology, University of California, Davis, CA, 95616, USA
- USDA-ARS, Crops Pathology and Genetics Research Unit, Davis, CA, 95616, USA
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69
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Tombesi S, Nardini A, Frioni T, Soccolini M, Zadra C, Farinelli D, Poni S, Palliotti A. Stomatal closure is induced by hydraulic signals and maintained by ABA in drought-stressed grapevine. Sci Rep 2015; 5:12449. [PMID: 26207993 PMCID: PMC4513549 DOI: 10.1038/srep12449] [Citation(s) in RCA: 132] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Accepted: 06/30/2015] [Indexed: 11/17/2022] Open
Abstract
Water saving under drought stress is assured by stomatal closure driven by active (ABA-mediated) and/or passive (hydraulic-mediated) mechanisms. There is currently no comprehensive model nor any general consensus about the actual contribution and relative importance of each of the above factors in modulating stomatal closure in planta. In the present study, we assessed the contribution of passive (hydraulic) vs active (ABA mediated) mechanisms of stomatal closure in V. vinifera plants facing drought stress. Leaf gas exchange decreased progressively to zero during drought, and embolism-induced loss of hydraulic conductance in petioles peaked to ~50% in correspondence with strong daily limitation of stomatal conductance. Foliar ABA significantly increased only after complete stomatal closure had already occurred. Rewatering plants after complete stomatal closure and after foliar ABA reached maximum values did not induced stomatal re-opening, despite embolism recovery and water potential rise. Our data suggest that in grapevine stomatal conductance is primarily regulated by passive hydraulic mechanisms. Foliar ABA apparently limits leaf gas exchange over long-term, also preventing recovery of stomatal aperture upon rewatering, suggesting the occurrence of a mechanism of long-term down-regulation of transpiration to favor embolism repair and preserve water under conditions of fluctuating water availability and repeated drought events.
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Affiliation(s)
- Sergio Tombesi
- Dipartimento di Scienze Agrarie, Alimentari e Ambientali, University of Perugia, Borgo 20 giugno 74, 06121 Perugia, Italy
| | - Andrea Nardini
- Dipartimento di Scienze della Vita, University of Trieste, Via L. Giorgieri 10, 34127 Trieste, Italy
| | - Tommaso Frioni
- Dipartimento di Scienze Agrarie, Alimentari e Ambientali, University of Perugia, Borgo 20 giugno 74, 06121 Perugia, Italy
| | - Marta Soccolini
- Dipartimento di Scienze Agrarie, Alimentari e Ambientali, University of Perugia, Borgo 20 giugno 74, 06121 Perugia, Italy
| | - Claudia Zadra
- Dipartimento di Scienze Farmaceutiche, University of Perugia, Borgo 20 giugno 74, 06121 Perugia, Italy
| | - Daniela Farinelli
- Dipartimento di Scienze Agrarie, Alimentari e Ambientali, University of Perugia, Borgo 20 giugno 74, 06121 Perugia, Italy
| | - Stefano Poni
- Dipartimento di Scienze delle Produzioni Vegetali Sostenibili, Università Cattolica del Sacro Cuore, Via E. Parmense 84, 29100 Piacenza, Italy
| | - Alberto Palliotti
- Dipartimento di Scienze Agrarie, Alimentari e Ambientali, University of Perugia, Borgo 20 giugno 74, 06121 Perugia, Italy
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70
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Ambrose AR, Baxter WL, Wong CS, Næsborg RR, Williams CB, Dawson TE. Contrasting drought-response strategies in California redwoods. TREE PHYSIOLOGY 2015; 35:453-469. [PMID: 25787330 DOI: 10.1093/treephys/tpv016] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 01/30/2015] [Indexed: 06/04/2023]
Abstract
We compared the physiology and growth of seedlings originating from different Sequoia sempervirens (D. Don.) Endl. (coast redwood) and Sequoiadendron giganteum (Lindl.) Buchh. (giant sequoia) populations subjected to progressive drought followed by a recovery period in a controlled greenhouse experiment. Our objective was to examine how multiple plant traits interact to influence the response of seedlings of each species and seed population to a single drought and recovery cycle. We measured soil and plant water status, leaf gas exchange, stem embolism and growth of control (well-watered) and drought-stressed (water withheld) seedlings from each population at the beginning, middle and end of a 6-week drought period and again 2 weeks after re-watering. The drought had a significant effect on many aspects of seedling performance, but water-stressed seedlings regained most physiological functioning by the end of the recovery period. Sequoiadendron seedlings exhibited a greater degree of isohydry (water status regulation), lower levels of stem embolism, higher biomass allocation to roots and lower sensitivity of growth to drought compared with Sequoia. Only minor intra-specific differences were observed among populations. Our results show that seedlings of the two redwood species exhibit contrasting drought-response strategies that align with the environmental conditions these trees experience in their native habitats, and demonstrate trade-offs and coordination among traits affecting plant water use, carbon gain and growth under drought.
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Affiliation(s)
- Anthony R Ambrose
- Department of Integrative Biology, University of California, Berkeley, CA 94720, USA
| | - Wendy L Baxter
- Department of Integrative Biology, University of California, Berkeley, CA 94720, USA
| | - Christopher S Wong
- Department of Integrative Biology, University of California, Berkeley, CA 94720, USA
| | - Rikke R Næsborg
- Department of Integrative Biology, University of California, Berkeley, CA 94720, USA
| | - Cameron B Williams
- Department of Integrative Biology, University of California, Berkeley, CA 94720, USA
| | - Todd E Dawson
- Department of Integrative Biology, University of California, Berkeley, CA 94720, USA
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71
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Simonin KA, Burns E, Choat B, Barbour MM, Dawson TE, Franks PJ. Increasing leaf hydraulic conductance with transpiration rate minimizes the water potential drawdown from stem to leaf. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:1303-15. [PMID: 25547915 PMCID: PMC4339593 DOI: 10.1093/jxb/eru481] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Leaf hydraulic conductance (k leaf) is a central element in the regulation of leaf water balance but the properties of k leaf remain uncertain. Here, the evidence for the following two models for k leaf in well-hydrated plants is evaluated: (i) k leaf is constant or (ii) k leaf increases as transpiration rate (E) increases. The difference between stem and leaf water potential (ΔΨstem-leaf), stomatal conductance (g s), k leaf, and E over a diurnal cycle for three angiosperm and gymnosperm tree species growing in a common garden, and for Helianthus annuus plants grown under sub-ambient, ambient, and elevated atmospheric CO₂ concentration were evaluated. Results show that for well-watered plants k leaf is positively dependent on E. Here, this property is termed the dynamic conductance, k leaf(E), which incorporates the inherent k leaf at zero E, which is distinguished as the static conductance, k leaf(0). Growth under different CO₂ concentrations maintained the same relationship between k leaf and E, resulting in similar k leaf(0), while operating along different regions of the curve owing to the influence of CO₂ on g s. The positive relationship between k leaf and E minimized variation in ΔΨstem-leaf. This enables leaves to minimize variation in Ψleaf and maximize g s and CO₂ assimilation rate over the diurnal course of evaporative demand.
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Affiliation(s)
- Kevin A Simonin
- Department of Biology, San Francisco State University, San Francisco, CA 94132, USA
| | - Emily Burns
- Save The Redwoods League, 111 Sutter Street, 11th Floor, San Francisco, CA 94104, USA
| | - Brendan Choat
- University of Western Sydney, Hawkesbury Institute for the Environment, Locked Bag 1797, Penrith 2751, NSW, Australia
| | - Margaret M Barbour
- Faculty of Agriculture and Environment, University of Sydney, NSW 2006, Australia
| | - Todd E Dawson
- Department of Integrative Biology, University of California-Berkeley, Berkeley, CA 94720, USA
| | - Peter J Franks
- Faculty of Agriculture and Environment, University of Sydney, NSW 2006, Australia
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72
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Martorell S, Medrano H, Tomàs M, Escalona JM, Flexas J, Diaz-Espejo A. Plasticity of vulnerability to leaf hydraulic dysfunction during acclimation to drought in grapevines: an osmotic-mediated process. PHYSIOLOGIA PLANTARUM 2015; 153:381-91. [PMID: 25132228 DOI: 10.1111/ppl.12253] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Revised: 05/28/2014] [Accepted: 06/11/2014] [Indexed: 05/04/2023]
Abstract
Previous studies have reported correlation of leaf hydraulic vulnerability with pressure-volume parameters related to cell turgor. This link has been explained on the basis of the effects of turgor on connectivity among cells and tissue structural integrity, which affect leaf water transport. In this study, we tested the hypothesis that osmotic adjustment to water stress would shift the leaf vulnerability curve toward more negative water potential (Ψ leaf ) by increasing turgor at low Ψ leaf . We measured leaf hydraulic conductance (K leaf ), K leaf vulnerability [50 and 80% loss of K leaf (P50 and P80 ); |Ψ leaf | at 50 and 80% loss of K leaf , respectively), bulk leaf water relations, leaf gas exchange and sap flow in two Vitis vinifera cultivars (Tempranillo and Grenache), under two water treatments. We found that P50 , P80 and maximum K leaf decreased seasonally by more than 20% in both cultivars and watering treatments. However, K leaf at 2 MPa increased threefold, while osmotic potential at full turgor and turgor loss point decreased. Our results indicate that leaf resistance to hydraulic dysfunction is seasonally plastic, and this plasticity may be mediated by osmotic adjustment.
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Affiliation(s)
- Sebastian Martorell
- Research Group on Plant Biology under Mediterranean Conditions, Departament de Biologia, Universitat de les Illes Balears, Palma de Mallorca, 07122, Spain
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73
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Choat B, Brodersen CR, McElrone AJ. Synchrotron X-ray microtomography of xylem embolism in Sequoia sempervirens saplings during cycles of drought and recovery. THE NEW PHYTOLOGIST 2015; 205:1095-1105. [PMID: 25385085 DOI: 10.1111/nph.13110] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Accepted: 09/10/2014] [Indexed: 05/23/2023]
Abstract
The formation of emboli in xylem conduits can dramatically reduce hydraulic capacity and represents one of the principal mechanisms of drought-induced mortality in woody plants. However, our understanding of embolism formation and repair is constrained by a lack of tools to directly and nondestructively measure these processes at high spatial resolution. Using synchrotron-based microcomputed tomography (microCT), we examined embolism in the xylem of coast redwood (Sequoia sempervirens) saplings that were subjected to cycles of drought and rewatering. Embolism formation was observed occurring by three different mechanisms: as tracheids embolizing in wide tangential bands; as isolated tracheids in seemingly random events; and as functional groups connected to photosynthetic organs. Upon rewatering, stem water potential recovered to predrought stress levels within 24 h; however, no evidence of embolism repair was observed even after a further 2 wk under well-watered conditions. The results indicate that intertracheid air seeding is the primary mechanism by which embolism spreads in the xylem of S. sempervirens, but also show that a small number of tracheids initially become gas-filled via another mechanism. The inability of S. sempervirens saplings to reverse drought-induced embolism is likely to have important ecological impacts on this species.
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Affiliation(s)
- Brendan Choat
- Hawkesbury Institute for the Environment, University of Western Sydney, Richmond, NSW, 2753, Australia
| | - Craig R Brodersen
- School of Forestry & Environmental Studies, Yale University, 195 Prospect Street, New Haven, CT, 06511, USA
| | - Andrew J McElrone
- USDA-Agricultural Research Service, Davis, CA, 95616, USA
- Department of Viticulture and Enology, University of California, Davis, CA, 95616, USA
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74
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Laur J, Hacke UG. The role of water channel proteins in facilitating recovery of leaf hydraulic conductance from water stress in Populus trichocarpa. PLoS One 2014; 9:e111751. [PMID: 25406088 PMCID: PMC4236056 DOI: 10.1371/journal.pone.0111751] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2014] [Accepted: 10/07/2014] [Indexed: 01/18/2023] Open
Abstract
Gas exchange is constrained by the whole-plant hydraulic conductance (Kplant). Leaves account for an important fraction of Kplant and may therefore represent a major determinant of plant productivity. Leaf hydraulic conductance (Kleaf) decreases with increasing water stress, which is due to xylem embolism in leaf veins and/or the properties of the extra-xylary pathway. Water flow through living tissues is facilitated and regulated by water channel proteins called aquaporins (AQPs). Here we assessed changes in the hydraulic conductance of Populus trichocarpa leaves during a dehydration-rewatering episode. While leaves were highly sensitive to drought, Kleaf recovered only 2 hours after plants were rewatered. Recovery of Kleaf was absent when excised leaves were bench-dried and subsequently xylem-perfused with a solution containing AQP inhibitors. We examined the expression patterns of 12 highly expressed AQP genes during a dehydration-rehydration episode to identify isoforms that may be involved in leaf hydraulic adjustments. Among the AQPs tested, several genes encoding tonoplast intrinsic proteins (TIPs) showed large increases in expression in rehydrated leaves, suggesting that TIPs contribute to reversing drought-induced reductions in Kleaf. TIPs were localized in xylem parenchyma, consistent with a role in facilitating water exchange between xylem vessels and adjacent living cells. Dye uptake experiments suggested that reversible embolism formation in minor leaf veins contributed to the observed changes in Kleaf.
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Affiliation(s)
- Joan Laur
- Department of Renewable Resources, University of Alberta, 442 Earth Sciences Building, Edmonton, Alberta, Canada
| | - Uwe G. Hacke
- Department of Renewable Resources, University of Alberta, 442 Earth Sciences Building, Edmonton, Alberta, Canada
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75
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Cano FJ, López R, Warren CR. Implications of the mesophyll conductance to CO2 for photosynthesis and water-use efficiency during long-term water stress and recovery in two contrasting Eucalyptus species. PLANT, CELL & ENVIRONMENT 2014; 37:2470-90. [PMID: 24635724 DOI: 10.1111/pce.12325] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Revised: 03/06/2014] [Accepted: 03/07/2014] [Indexed: 05/26/2023]
Abstract
Water stress (WS) slows growth and photosynthesis (A(n)), but most knowledge comes from short-time studies that do not account for longer term acclimation processes that are especially relevant in tree species. Using two Eucalyptus species that contrast in drought tolerance, we induced moderate and severe water deficits by withholding water until stomatal conductance (g(sw)) decreased to two pre-defined values for 24 d, WS was maintained at the target g(sw) for 29 d and then plants were re-watered. Additionally, we developed new equations to simulate the effect on mesophyll conductance (g(m)) of accounting for the resistance to refixation of CO(2). The diffusive limitations to CO(2), dominated by the stomata, were the most important constraints to A(n). Full recovery of A(n) was reached after re-watering, characterized by quick recovery of gm and even higher biochemical capacity, in contrast to the slower recovery of g(sw). The acclimation to long-term WS led to decreased mesophyll and biochemical limitations, in contrast to studies in which stress was imposed more rapidly. Finally, we provide evidence that higher gm under WS contributes to higher intrinsic water-use efficiency (iWUE) and reduces the leaf oxidative stress, highlighting the importance of gm as a target for breeding/genetic engineering.
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Affiliation(s)
- F Javier Cano
- Unidad Docente de Anatomía, Fisiología y Genética Forestal, E.T.S.I. Montes, Universidad Politécnica de Madrid (UPM), 28040, Madrid, Spain
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76
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Secchi F, Zwieniecki MA. Down-regulation of plasma intrinsic protein1 aquaporin in poplar trees is detrimental to recovery from embolism. PLANT PHYSIOLOGY 2014; 164:1789-99. [PMID: 24572173 PMCID: PMC3982741 DOI: 10.1104/pp.114.237511] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Accepted: 02/25/2014] [Indexed: 05/18/2023]
Abstract
During their lifecycles, trees encounter multiple events of water stress that often result in embolism formation and temporal decreases in xylem transport capacity. The restoration of xylem transport capacity requires changes in cell metabolic activity and gene expression. Specifically, in poplar (Populus spp.), the formation of xylem embolisms leads to a clear up-regulation of plasma membrane protein1 (PIP1) aquaporin genes. To determine their role in poplar response to water stress, transgenic Populus tremula × Populus alba plants characterized by the strong down-regulation of multiple isoforms belonging to the PIP1 subfamily were used. Transgenic lines showed that they are more vulnerable to embolism, with 50% percent loss of conductance occurring 0.3 MPa earlier than in wild-type plants, and that they also have a reduced capacity to restore xylem conductance during recovery. Transgenic plants also show symptoms of a reduced capacity to control percent loss of conductance through stomatal conductance in response to drought, because they have a much narrower vulnerability safety margin. Finally, a delay in stomatal conductance recovery during the period of stress relief was observed. The presented results suggest that PIP1 genes are involved in the maintenance of xylem transport system capacity, in the promotion of recovery from stress, and in contribution to a plant's control of stomatal conductance under water stress.
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