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Ogée J. A step forward in the study of photosynthetic limitation by CO 2 diffusion into the mesophyll. THE NEW PHYTOLOGIST 2024. [PMID: 38887143 DOI: 10.1111/nph.19910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2024]
Affiliation(s)
- Jérôme Ogée
- INRAE, Bordeaux Science Agro, UMR 1391 ISPA, Villenave d'Ornon, 33140, France
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2
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Cernusak LA, Wong SC, Stuart-Williams H, Márquez DA, Pontarin N, Farquhar GD. Unsaturation in the air spaces of leaves and its implications. PLANT, CELL & ENVIRONMENT 2024. [PMID: 38867619 DOI: 10.1111/pce.15001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2024] [Revised: 05/26/2024] [Accepted: 05/31/2024] [Indexed: 06/14/2024]
Abstract
Modern plant physiological theory stipulates that the resistance to water movement from plants to the atmosphere is overwhelmingly dominated by stomata. This conception necessitates a corollary assumption-that the air spaces in leaves must be nearly saturated with water vapour; that is, with a relative humidity that does not decline materially below unity. As this idea became progressively engrained in scientific discourse and textbooks over the last century, observations inconsistent with this corollary assumption were occasionally reported. Yet, evidence of unsaturation gained little traction, with acceptance of the prevailing framework motivated by three considerations: (1) leaf water potentials measured by either thermocouple psychrometry or the Scholander pressure chamber are largely consistent with the framework; (2) being able to assume near saturation of intercellular air spaces was transformational to leaf gas exchange analysis; and (3) there has been no obvious mechanism to explain a variable, liquid-phase resistance in the leaf mesophyll. Here, we review the evidence that refutes the assumption of universal, near saturation of air spaces in leaves. Refining the prevailing paradigm with respect to this assumption provides opportunities for identifying and developing mechanisms for increased plant productivity in the face of increasing evaporative demand imposed by global climate change.
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Affiliation(s)
- Lucas A Cernusak
- College of Science and Engineering, James Cook University, Cairns, Queensland, Australia
| | - Suan Chin Wong
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Hilary Stuart-Williams
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Diego A Márquez
- School of Biosciences, University of Birmingham, Birmingham, UK
| | - Nicole Pontarin
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Graham D Farquhar
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia
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3
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Aryal S, Grießinger J, Gaire NP, Bhattarai T, Bräuning A. Drought, temperature, and moisture availability: understanding the drivers of isotopic decoupling in native pine species of the Nepalese Himalaya. INTERNATIONAL JOURNAL OF BIOMETEOROLOGY 2024; 68:1093-1108. [PMID: 38441667 PMCID: PMC11108894 DOI: 10.1007/s00484-024-02647-z] [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: 06/25/2023] [Revised: 02/12/2024] [Accepted: 02/28/2024] [Indexed: 05/22/2024]
Abstract
The Himalayas experienced long-term climate changes and recent extreme weather events that affected plant growth and the physiology of tree species at high-elevation sites. This study presents the first statistically robust δ18OTR chronologies for two native pine species, Pinus roxburghii, and Pinus wallichiana, in the lower Nepalese Himalaya. The isotope chronologies exhibited 0.88‰ differences in overall mean isotope values attributed to varying elevations (460-2000 m asl). Comparative analysis of climate response using data sets from different sources and resolutions revealed the superiority of the APHRODITE (Asian Precipitation - Highly-Resolved Observational Data Integration Towards Evaluation) data set calibrated for the South Asian Summer Monsoon (SASM)-dominated region. Both species exhibited negative correlations with monsoon precipitation and positive correlations with temperature. However, during the peak monsoon season (July-August), daily resolved climate data disentangled statistically insignificant relationships, and revealed that δ18OTR is influenced by atmospheric moisture. Both congeneric species showed a decoupling between the chronologies after 1995. However, no significant change in air moisture origin and monsoon regime between the study sites was observed, indicating a consistent dominant moisture source during different monsoon seasons. Besides, we also observed the decreased inter-series correlation of both δ18OTR chronologies after 1995, with P. wallichiana experiencing a steeper decrease than P. roxburghii. The weakening correlations between and within the chronologies coincided with a regional drought during 1993-1995 in both sites, highlighting the strong regulation of local climate on the impact of regional extreme climate events. Our findings emphasise the importance of employing climate data with optimal spatial and temporal resolution for improved δ18OTR-climate relationships at the intra-annual scale while considering the influence of site-specific local environmental conditions. Assessing climate data sets with station data is vital for accurately interpreting climate change's impact on forest response and long-term climate reconstructions.
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Affiliation(s)
- Sugam Aryal
- Institute für Geographie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Wetterkreuz 15, 91058, Erlangen, Germany.
| | - Jussi Grießinger
- Institute für Geographie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Wetterkreuz 15, 91058, Erlangen, Germany
- Department of Environment and Biodiversity, University Salzburg, Salzburg, Austria
| | | | | | - Achim Bräuning
- Institute für Geographie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Wetterkreuz 15, 91058, Erlangen, Germany
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4
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Mercado-Reyes JA, Pereira TS, Manandhar A, Rimer IM, McAdam SAM. Extreme drought can deactivate ABA biosynthesis in embolism-resistant species. PLANT, CELL & ENVIRONMENT 2024; 47:497-510. [PMID: 37905689 DOI: 10.1111/pce.14754] [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: 03/25/2022] [Revised: 08/24/2023] [Accepted: 10/18/2023] [Indexed: 11/02/2023]
Abstract
The phytohormone abscisic acid (ABA) is synthesised by plants during drought to close stomata and regulate desiccation tolerance pathways. Conifers and some angiosperms with embolism-resistant xylem show a peaking-type (p-type) response in ABA levels, in which ABA levels increase early in drought then decrease as drought progresses, declining to pre-stressed levels. The mechanism behind this dynamic remains unknown. Here, we sought to characterise the mechanism driving p-type ABA dynamics in the conifer Callitris rhomboidea and the highly drought-resistant angiosperm Umbellularia californica. We measured leaf water potentials (Ψl ), stomatal conductance, ABA, conjugates and phaseic acid (PA) levels in potted plants during a prolonged but non-fatal drought. Both species displayed a p-type ABA dynamic during prolonged drought. In branches collected before and after the peak in endogenous ABA levels in planta, that were rehydrated overnight and then bench dried, ABA biosynthesis was deactivated beyond leaf turgor loss point. Considerable conversion of ABA to conjugates was found to occur during drought, but not catabolism to PA. The mechanism driving the decline in ABA levels in p-type species may be conserved across embolism-resistant seed plants and is mediated by sustained conjugation of ABA and the deactivation of ABA accumulation as Ψl becomes more negative than turgor loss.
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Affiliation(s)
- Joel A Mercado-Reyes
- Purdue Center for Plant Biology, Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, USA
| | - Talitha Soares Pereira
- Purdue Center for Plant Biology, Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, USA
| | - Anju Manandhar
- Purdue Center for Plant Biology, Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, USA
| | - Ian M Rimer
- Purdue Center for Plant Biology, Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, USA
| | - Scott A M McAdam
- Purdue Center for Plant Biology, Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, USA
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5
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Binstock BR, Manandhar A, McAdam SAM. Characterizing the breakpoint of stomatal response to vapor pressure deficit in an angiosperm. PLANT PHYSIOLOGY 2024; 194:732-740. [PMID: 37850913 DOI: 10.1093/plphys/kiad560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 09/21/2023] [Accepted: 10/05/2023] [Indexed: 10/19/2023]
Abstract
Vapor pressure difference between the leaf and atmosphere (VPD) is the most important regulator of daytime transpiration, yet the mechanism driving stomatal responses to an increase in VPD in angiosperms remains unresolved. Here, we sought to characterize the mechanism driving stomatal closure at high VPD in an angiosperm species, particularly testing whether abscisic acid (ABA) biosynthesis could explain the observation of a trigger point for stomatal sensitivity to an increase in VPD. We tracked leaf gas exchange and modeled leaf water potential (Ψl) in leaves exposed to a range of step-increases in VPD in the herbaceous species Senecio minimus Poir. (Asteraceae). We found that mild increases in VPD in this species did not induce stomatal closure because modeled Ψl did not decline below a threshold close to turgor loss point (Ψtlp), but when leaves were exposed to a large increase in VPD, stomata closed as modeled Ψl declined below Ψtlp. Leaf ABA levels were higher in leaves exposed to a step-increase in VPD that caused Ψl to transiently decline below Ψtlp and in which stomata closed compared with leaves in which stomata did not close. We conclude that the stomata of S. minimus are insensitive to VPD until Ψl declines to a threshold that triggers the biosynthesis of ABA and that this mechanism might be common to angiosperms.
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Affiliation(s)
- Benjamin R Binstock
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, USA
| | - Anju Manandhar
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, USA
| | - Scott A M McAdam
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, USA
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6
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Mok D, Leung A, Searles P, Sage TL, Sage RF. CAM photosynthesis in Bulnesia retama (Zygophyllaceae), a non-succulent desert shrub from South America. ANNALS OF BOTANY 2023; 132:655-670. [PMID: 37625031 PMCID: PMC10799978 DOI: 10.1093/aob/mcad114] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 07/19/2023] [Accepted: 08/23/2023] [Indexed: 08/27/2023]
Abstract
BACKGROUND AND AIMS Bulnesia retama is a drought-deciduous, xerophytic shrub from arid landscapes of South America. In a survey of carbon isotope ratios (δ13C) in specimens from the field, B. retama exhibited less negative values, indicative of CAM or C4 photosynthesis. Here, we investigate whether B. retama is a C4 or CAM plant. METHODS Gas-exchange responses to intercellular CO2, diurnal gas-exchange profiles, δ13C and dawn vs. afternoon titratable acidity were measured on leaves and stems of watered and droughted B. retama plants. Leaf and stem cross-sections were imaged to determine whether the tissues exhibited succulent CAM or C4 Kranz anatomy. KEY RESULTS Field-collected stems and fruits of B. retama exhibited δ13C between -16 and -19 ‰. Plants grown in a glasshouse from field-collected seeds had leaf δ13C values near -31 ‰ and stem δ13C values near -28 ‰. The CO2 response of photosynthesis showed that leaves and stems used C3 photosynthesis during the day, while curvature in the nocturnal response of net CO2 assimilation rate (A) in all stems, coupled with slightly positive rates of A at night, indicated modest CAM function. C4 photosynthesis was absent. Succulence was absent in all tissues, although stems exhibited tight packing of the cortical chlorenchyma in a CAM-like manner. Tissue titratable acidity increased at night in droughted stems. CONCLUSIONS Bulnesia retama is a weak to modest C3 + CAM plant. This is the first report of CAM in the Zygophyllaceae and the first showing that non-succulent, xerophytic shrubs use CAM. CAM alone in B. retama was too limited to explain less negative δ13C in field-collected plants, but combined with effects of low stomatal and mesophyll conductance it could raise δ13C to observed values between -16 and -19 ‰. Modest CAM activity, particularly during severe drought, could enable B. retama to persist in arid habitats of South America.
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Affiliation(s)
- Daniel Mok
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Wilcocks Street, Toronto, Ontario M5R3C6, Canada
| | - Arthur Leung
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Wilcocks Street, Toronto, Ontario M5R3C6, Canada
| | - Peter Searles
- Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja (CRILAR-CONICET), Entre Ríos y Mendoza s/n, Anillaco (5301), La Rioja, Argentina
| | - Tammy L Sage
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Wilcocks Street, Toronto, Ontario M5R3C6, Canada
| | - Rowan F Sage
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Wilcocks Street, Toronto, Ontario M5R3C6, Canada
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7
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Scoffoni C, Albuquerque C, Buckley TN, Sack L. The dynamic multi-functionality of leaf water transport outside the xylem. THE NEW PHYTOLOGIST 2023; 239:2099-2107. [PMID: 37386735 DOI: 10.1111/nph.19069] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2022] [Accepted: 05/12/2023] [Indexed: 07/01/2023]
Abstract
A surge of papers have reported low leaf vulnerability to xylem embolism during drought. Here, we focus on the less studied, and more sensitive, outside-xylem leaf hydraulic responses to multiple internal and external conditions. Studies of 34 species have resolved substantial vulnerability to dehydration of the outside-xylem pathways, and studies of leaf hydraulic responses to light also implicate dynamic outside-xylem responses. Detailed experiments suggest these dynamic responses arise at least in part from strong control of radial water movement across the vein bundle sheath. While leaf xylem vulnerability may influence leaf and plant survival during extreme drought, outside-xylem dynamic responses are important for the control and resilience of water transport and leaf water status for gas exchange and growth.
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Affiliation(s)
- Christine Scoffoni
- Department of Biological Sciences, California State University Los Angeles, 5151 State University Dr., Los Angeles, CA, 90032, USA
| | - Caetano Albuquerque
- Department of Biological Sciences, California State University Los Angeles, 5151 State University Dr., Los Angeles, CA, 90032, USA
| | - Thomas N Buckley
- Department of Plant Sciences, University of California, Davis, 1 Shields Ave, Davis, CA, 95616, USA
| | - Lawren Sack
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, 612 Charles E. Young Dr., Los Angeles, CA, 90095, USA
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8
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Tulva I, Välbe M, Merilo E. Plants lacking OST1 show conditional stomatal closure and wildtype-like growth sensitivity at high VPD. PHYSIOLOGIA PLANTARUM 2023; 175:e14030. [PMID: 37882302 DOI: 10.1111/ppl.14030] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Revised: 08/24/2023] [Accepted: 09/06/2023] [Indexed: 10/27/2023]
Abstract
Climate change-associated rise in VPD (atmospheric vapor pressure deficit) results in increased plant transpiration and reduced stomatal conductance, photosynthesis, biomass, and yield. High VPD-induced stomatal closure of Arabidopsis is an active process regulated via the kinase SnRK2.6 (OPEN STOMATA 1, OST1). Here, we performed gas exchange, leaf water potential and rosette growth measurements to study, whether (1) high VPD-induced stomatal closure is detected in plants carrying loss-of-function mutations in OST1 (ost1-3) when they are grown at reduced soil water content or measured at increased air temperature; (2) ost1-3 plants expressing OST1 construct with no ABA-activation domain, but intact ABA-independent activation, show stronger stomatal VPD response compared with ost1-3 plants; and (3) rosette area and biomass of ost1-3 are more affected by growth at high VPD compared with Col-0. The stomata of well-watered ost1-3 plants were insensitive to high VPD regardless of air temperature, but in deficit-irrigated ost1-3, leaf water potential decreased the most and stomata closed at high VPD. Differences between VPD-induced stomatal closures of ost1-3 plants and ost1-3 plants expressing OST1 with no ABA-activation domain point at gradual VPD-induced ABA-independent activation of OST1. High VPD conditions led to similar reductions in rosette area and specific leaf area of well-watered Col-0 and ost1-3 plants. Rosette dry mass was unaffected by high VPD. Our results show that OST1 loss-of-function plants display conditional stomatal closure and no extra sensitivity of rosette area growth compared with Col-0 wildtype under high VPD conditions.
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Affiliation(s)
- Ingmar Tulva
- Institute of Technology, University of Tartu, Tartu, Estonia
| | - Mikk Välbe
- Institute of Technology, University of Tartu, Tartu, Estonia
| | - Ebe Merilo
- Institute of Technology, University of Tartu, Tartu, Estonia
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9
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Zhong Z, He B, Wang YP, Chen HW, Chen D, Fu YH, Chen Y, Guo L, Deng Y, Huang L, Yuan W, Hao X, Tang R, Liu H, Sun L, Xie X, Zhang Y. Disentangling the effects of vapor pressure deficit on northern terrestrial vegetation productivity. SCIENCE ADVANCES 2023; 9:eadf3166. [PMID: 37556542 PMCID: PMC10411893 DOI: 10.1126/sciadv.adf3166] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 07/07/2023] [Indexed: 08/11/2023]
Abstract
The impact of atmospheric vapor pressure deficit (VPD) on plant photosynthesis has long been acknowledged, but large interactions with air temperature (T) and soil moisture (SM) still hinder a complete understanding of the influence of VPD on vegetation production across various climate zones. Here, we found a diverging response of productivity to VPD in the Northern Hemisphere by excluding interactive effects of VPD with T and SM. The interactions between VPD and T/SM not only offset the potential positive impact of warming on vegetation productivity but also amplifies the negative effect of soil drying. Notably, for high-latitude ecosystems, there occurs a pronounced shift in vegetation productivity's response to VPD during the growing season when VPD surpasses a threshold of 3.5 to 4.0 hectopascals. These results yield previously unknown insights into the role of VPD in terrestrial ecosystems and enhance our comprehension of the terrestrial carbon cycle's response to global warming.
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Affiliation(s)
- Ziqian Zhong
- State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, 100875 Beijing, China
| | - Bin He
- State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, 100875 Beijing, China
| | - Ying-Ping Wang
- CSIRO Environment, Private Bag 1, Aspendale, Victoria, Australia
| | - Hans W. Chen
- Department of Space, Earth and Environment, Division of Geoscience and Remote Sensing, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
| | - Deliang Chen
- Regional Climate Group, Department of Earth Sciences, University of Gothenburg, S-40530 Gothenburg, Sweden
| | - Yongshuo H. Fu
- College of Water Sciences, Beijing Normal University, 100875 Beijing, China
| | - Yaning Chen
- State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, 830011 Urumqi, China
| | - Lanlan Guo
- School of Geography, Beijing Normal University, 100875 Beijing, China
| | - Ying Deng
- State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, No. 20 Nanxincun, Xiangshan, 100093 Beijing, China
| | - Ling Huang
- College of Urban and Environmental Sciences, Peking University, 100871 Beijing, China
| | - Wenping Yuan
- School of Atmospheric Sciences, Sun Yat-Sen University, 510275 Guangzhou, China
| | - Xingmin Hao
- State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, 830011 Urumqi, China
| | - Rui Tang
- State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, 100875 Beijing, China
| | - Huiming Liu
- Ministry of Ecology and Environment Center for Satellite Application on Ecology and Environment, 100094 Beijing, China
| | - Liying Sun
- Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, 100101 Beijing, China
| | - Xiaoming Xie
- State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, 100875 Beijing, China
| | - Yafeng Zhang
- State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, 100875 Beijing, China
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10
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Rockwell FE, Holbrook NM, Jain P, Huber AE, Sen S, Stroock AD. Extreme undersaturation in the intercellular airspace of leaves: a failure of Gaastra or Ohm? ANNALS OF BOTANY 2022; 130:301-316. [PMID: 35896037 PMCID: PMC9486918 DOI: 10.1093/aob/mcac094] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 07/21/2022] [Indexed: 06/09/2023]
Abstract
BACKGROUND Recent reports of extreme levels of undersaturation in internal leaf air spaces have called into question one of the foundational assumptions of leaf gas exchange analysis, that leaf air spaces are effectively saturated with water vapour at leaf surface temperature. Historically, inferring the biophysical states controlling assimilation and transpiration from the fluxes directly measured by gas exchange systems has presented a number of challenges, including: (1) a mismatch in scales between the area of flux measurement, the biochemical cellular scale and the meso-scale introduced by the localization of the fluxes to stomatal pores; (2) the inaccessibility of the internal states of CO2 and water vapour required to define conductances; and (3) uncertainties about the pathways these internal fluxes travel. In response, plant physiologists have adopted a set of simplifying assumptions that define phenomenological concepts such as stomatal and mesophyll conductances. SCOPE Investigators have long been concerned that a failure of basic assumptions could be distorting our understanding of these phenomenological conductances, and the biophysical states inside leaves. Here we review these assumptions and historical efforts to test them. We then explore whether artefacts in analysis arising from the averaging of fluxes over macroscopic leaf areas could provide alternative explanations for some part, if not all, of reported extreme states of undersaturation. CONCLUSIONS Spatial heterogeneities can, in some cases, create the appearance of undersaturation in the internal air spaces of leaves. Further refinement of experimental approaches will be required to separate undersaturation from the effects of spatial variations in fluxes or conductances. Novel combinations of current and emerging technologies hold promise for meeting this challenge.
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Affiliation(s)
| | - N Michele Holbrook
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Piyush Jain
- School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, USA
| | - Annika E Huber
- School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, USA
| | - Sabyasachi Sen
- School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, USA
| | - Abraham D Stroock
- School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, USA
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11
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Wong SC, Canny MJ, Holloway-Phillips M, Stuart-Williams H, Cernusak LA, Márquez DA, Farquhar GD. Humidity gradients in the air spaces of leaves. NATURE PLANTS 2022; 8:971-978. [PMID: 35941216 DOI: 10.1038/s41477-022-01202-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Accepted: 06/22/2022] [Indexed: 06/15/2023]
Abstract
Stomata are orifices that connect the drier atmosphere with the interconnected network of more humid air spaces that surround the cells within a leaf. Accurate values of the humidities inside the substomatal cavity, wi, and in the air, wa, are needed to estimate stomatal conductance and the CO2 concentration in the internal air spaces of leaves. Both are vital factors in the understanding of plant physiology and climate, ecological and crop systems. However, there is no easy way to measure wi directly. Out of necessity, wi has been taken as the saturation water vapour concentration at leaf temperature, wsat, and applied to the whole leaf intercellular air spaces. We explored the occurrence of unsaturation by examining gas exchange of leaves exposed to various magnitudes of wsat - wa, or Δw, using a double-sided, clamp-on chamber, and estimated degrees of unsaturation from the gradient of CO2 across the leaf that was required to sustain the rate of CO2 assimilation through the upper surface. The relative humidity in the substomatal cavities dropped to about 97% under mild Δw and as dry as around 80% when Δw was large. Measurements of the diffusion of noble gases across the leaf indicated that there were still regions of near 100% humidity distal from the stomatal pores. We suggest that as Δw increases, the saturation edge retreats into the intercellular air spaces, accompanied by the progressive closure of mesophyll aquaporins to maintain the cytosolic water potential.
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Affiliation(s)
- Suan Chin Wong
- Plant Sciences, Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Martin J Canny
- Plant Sciences, Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Meisha Holloway-Phillips
- Plant Sciences, Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia
- Physiological Plant Ecology Group, Department of Environmental Sciences-Botany, University of Basel, Basel, Switzerland
| | - Hilary Stuart-Williams
- Plant Sciences, Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Lucas A Cernusak
- College of Science and Engineering, James Cook University, Cairns, Queensland, Australia
| | - Diego A Márquez
- Plant Sciences, Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Graham D Farquhar
- Plant Sciences, Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia.
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12
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Cernusak LA, Barbeta A, Bush RT, Eichstaedt (Bögelein) R, Ferrio JP, Flanagan LB, Gessler A, Martín‐Gómez P, Hirl RT, Kahmen A, Keitel C, Lai C, Munksgaard NC, Nelson DB, Ogée J, Roden JS, Schnyder H, Voelker SL, Wang L, Stuart‐Williams H, Wingate L, Yu W, Zhao L, Cuntz M. Do 2 H and 18 O in leaf water reflect environmental drivers differently? THE NEW PHYTOLOGIST 2022; 235:41-51. [PMID: 35322882 PMCID: PMC9322340 DOI: 10.1111/nph.18113] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 02/06/2022] [Indexed: 06/01/2023]
Abstract
We compiled hydrogen and oxygen stable isotope compositions (δ2 H and δ18 O) of leaf water from multiple biomes to examine variations with environmental drivers. Leaf water δ2 H was more closely correlated with δ2 H of xylem water or atmospheric vapour, whereas leaf water δ18 O was more closely correlated with air relative humidity. This resulted from the larger proportional range for δ2 H of meteoric waters relative to the extent of leaf water evaporative enrichment compared with δ18 O. We next expressed leaf water as isotopic enrichment above xylem water (Δ2 H and Δ18 O) to remove the impact of xylem water isotopic variation. For Δ2 H, leaf water still correlated with atmospheric vapour, whereas Δ18 O showed no such correlation. This was explained by covariance between air relative humidity and the Δ18 O of atmospheric vapour. This is consistent with a previously observed diurnal correlation between air relative humidity and the deuterium excess of atmospheric vapour across a range of ecosystems. We conclude that 2 H and 18 O in leaf water do indeed reflect the balance of environmental drivers differently; our results have implications for understanding isotopic effects associated with water cycling in terrestrial ecosystems and for inferring environmental change from isotopic biomarkers that act as proxies for leaf water.
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Affiliation(s)
- Lucas A. Cernusak
- College of Science and EngineeringJames Cook UniversityCairnsQld4878Australia
| | - Adrià Barbeta
- BEECADepartment of Evolutionary Biology, Ecology and Environmental SciencesUniversitat de BarcelonaBarcelonaCatalonia08028Spain
| | - Rosemary T. Bush
- Department of Earth and Planetary SciencesNorthwestern UniversityEvanstonIL60208USA
| | | | - Juan Pedro Ferrio
- ARAID‐Departamento de Sistemas AgrícolasForestales y Medio AmbienteCentro de Investigación y Tecnología Agroalimentaria de Aragón (CITA)Zaragoza50059Spain
| | - Lawrence B. Flanagan
- Department of Biological SciencesUniversity of LethbridgeLethbridgeABT1K 3M4Canada
| | - Arthur Gessler
- WSL Swiss Federal Institute for Forest, Snow and Landscape ResearchBirmensdorf8903Switzerland
| | - Paula Martín‐Gómez
- INRAEBordeaux Sciences AgroUMR ISPAVillenave d'Ornon 33140France
- Centre Tecnològic Forestal de Catalunya (CTFC)SolsonaCatalonia25280Spain
| | - Regina T. Hirl
- Technische Universität MünchenLehrstuhl für GrünlandlehreFreising‐Weihenstephan85354Germany
| | - Ansgar Kahmen
- Department of Environmental Sciences–BotanyUniversity of BaselBasel4056Switzerland
| | - Claudia Keitel
- School of Life and Environmental SciencesSydney Institute of AgricultureThe University of SydneyCamdenNSW2006Australia
| | - Chun‐Ta Lai
- Department of BiologySan Diego State UniversitySan DiegoCA92182USA
| | - Niels C. Munksgaard
- College of Science and EngineeringJames Cook UniversityCairnsQld4878Australia
| | - Daniel B. Nelson
- Department of Environmental Sciences–BotanyUniversity of BaselBasel4056Switzerland
| | - Jérôme Ogée
- INRAEBordeaux Sciences AgroUMR ISPAVillenave d'Ornon 33140France
| | - John S. Roden
- Department of BiologySouthern Oregon UniversityAshlandOR97520USA
| | - Hans Schnyder
- Technische Universität MünchenLehrstuhl für GrünlandlehreFreising‐Weihenstephan85354Germany
| | - Steven L. Voelker
- College of Forest Resources and Environmental ScienceMichigan Technological UniversityHoughtonMI49931USA
| | - Lixin Wang
- Department of Earth SciencesIndiana University–Purdue University IndianapolisIndianapolisIND46202USA
| | | | - Lisa Wingate
- INRAEBordeaux Sciences AgroUMR ISPAVillenave d'Ornon 33140France
| | - Wusheng Yu
- Key Laboratory of Tibetan Environmental Changes and Land Surface ProcessesInstitute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing100101China
| | - Liangju Zhao
- Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying CapacityCollege of Urban and Environmental SciencesNorthwest UniversityXi'an 710127China
| | - Matthias Cuntz
- Université de LorraineAgroParisTechINRAEUMR SilvaNancy54000France
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13
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Hsu PK, Takahashi Y, Merilo E, Costa A, Zhang L, Kernig K, Lee KH, Schroeder JI. Raf-like kinases and receptor-like (pseudo)kinase GHR1 are required for stomatal vapor pressure difference response. Proc Natl Acad Sci U S A 2021; 118:e2107280118. [PMID: 34799443 PMCID: PMC8617523 DOI: 10.1073/pnas.2107280118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/30/2021] [Indexed: 12/19/2022] Open
Abstract
Stomatal pores close rapidly in response to low-air-humidity-induced leaf-to-air vapor pressure difference (VPD) increases, thereby reducing excessive water loss. The hydroactive signal-transduction mechanisms mediating high VPD-induced stomatal closure remain largely unknown. The kinetics of stomatal high-VPD responses were investigated by using time-resolved gas-exchange analyses of higher-order mutants in guard-cell signal-transduction branches. We show that the slow-type anion channel SLAC1 plays a relatively more substantial role than the rapid-type anion channel ALMT12/QUAC1 in stomatal VPD signaling. VPD-induced stomatal closure is not affected in mpk12/mpk4GC double mutants that completely disrupt stomatal CO2 signaling, indicating that VPD signaling is independent of the early CO2 signal-transduction pathway. Calcium imaging shows that osmotic stress causes cytoplasmic Ca2+ transients in guard cells. Nevertheless, osca1-2/1.3/2.2/2.3/3.1 Ca2+-permeable channel quintuple, osca1.3/1.7-channel double, cngc5/6-channel double, cngc20-channel single, cngc19/20crispr-channel double, glr3.2/3.3-channel double, cpk-kinase quintuple, cbl1/4/5/8/9 quintuple, and cbl2/3rf double mutants showed wild-type-like stomatal VPD responses. A B3-family Raf-like mitogen-activated protein (MAP)-kinase kinase kinase, M3Kδ5/RAF6, activates the OST1/SnRK2.6 kinase in plant cells. Interestingly, B3 Raf-kinase m3kδ5 and m3kδ1/δ5/δ6/δ7 (raf3/6/5/4) quadruple mutants, but not a 14-gene raf-kinase mutant including osmotic stress-linked B4-family Raf-kinases, exhibited slowed high-VPD responses, suggesting that B3-family Raf-kinases play an important role in stomatal VPD signaling. Moreover, high VPD-induced stomatal closure was impaired in receptor-like pseudokinase GUARD CELL HYDROGEN PEROXIDE-RESISTANT1 (GHR1) mutant alleles. Notably, the classical transient "wrong-way" VPD response was absent in ghr1 mutant alleles. These findings reveal genes and signaling mechanisms in the elusive high VPD-induced stomatal closing response pathway.
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Affiliation(s)
- Po-Kai Hsu
- Cell and Developmental Biology Section, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093
| | - Yohei Takahashi
- Cell and Developmental Biology Section, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093
| | - Ebe Merilo
- Institute of Technology, University of Tartu, Tartu 50411, Estonia
| | - Alex Costa
- Cell and Developmental Biology Section, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093
- Department of Biosciences, University of Milan, Milan 20133, Italy
- Institute of Biophysics, Consiglio Nazionale delle Ricerche, 20133 Milan, Italy
| | - Li Zhang
- Cell and Developmental Biology Section, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093
| | - Klara Kernig
- Cell and Developmental Biology Section, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093
| | - Katie H Lee
- Cell and Developmental Biology Section, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093
| | - Julian I Schroeder
- Cell and Developmental Biology Section, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093;
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14
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Dusenge ME, Wittemann M, Mujawamariya M, Ntawuhiganayo EB, Zibera E, Ntirugulirwa B, Way DA, Nsabimana D, Uddling J, Wallin G. Limited thermal acclimation of photosynthesis in tropical montane tree species. GLOBAL CHANGE BIOLOGY 2021; 27:4860-4878. [PMID: 34233063 DOI: 10.1111/gcb.15790] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 06/21/2021] [Accepted: 06/28/2021] [Indexed: 06/13/2023]
Abstract
The temperature sensitivity of physiological processes and growth of tropical trees remains a key uncertainty in predicting how tropical forests will adjust to future climates. In particular, our knowledge regarding warming responses of photosynthesis, and its underlying biochemical mechanisms, is very limited. We grew seedlings of two tropical montane rainforest tree species, the early-successional species Harungana montana and the late-successional species Syzygium guineense, at three different sites along an elevation gradient, differing by 6.8℃ in daytime ambient air temperature. Their physiological and growth performance was investigated at each site. The optimum temperature of net photosynthesis (ToptA ) did not significantly increase in warm-grown trees in either species. Similarly, the thermal optima (ToptV and ToptJ ) and activation energies (EaV and EaJ ) of maximum Rubisco carboxylation capacity (Vcmax ) and maximum electron transport rate (Jmax ) were largely unaffected by warming. However, Vcmax , Jmax and foliar dark respiration (Rd ) at 25℃ were significantly reduced by warming in both species, and this decline was partly associated with concomitant reduction in total leaf nitrogen content. The ratio of Jmax /Vcmax decreased with increasing leaf temperature for both species, but the ratio at 25℃ was constant across sites. Furthermore, in H. montana, stomatal conductance at 25℃ remained constant across the different temperature treatments, while in S. guineense it increased with warming. Total dry biomass increased with warming in H. montana but remained constant in S. guineense. The biomass allocated to roots, stem and leaves was not affected by warming in H. montana, whereas the biomass allocated to roots significantly increased in S. guineense. Overall, our findings show that in these two tropical montane rainforest tree species, the capacity to acclimate the thermal optimum of photosynthesis is limited while warming-induced reductions in respiration and photosynthetic capacity rates are tightly coupled and linked to responses of leaf nitrogen.
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Affiliation(s)
- Mirindi Eric Dusenge
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
- School of Forestry, Biodiversity and Biological Sciences, College of Agriculture, Animal Sciences and Veterinary Medicine, University of Rwanda, Musanze, Rwanda
- Department of Biology, The University of Western Ontario, London, ON, Canada
- Gothenburg Global Biodiversity Centre (GGBC), University of Gothenburg, Gothenburg, Sweden
| | - Maria Wittemann
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
- Gothenburg Global Biodiversity Centre (GGBC), University of Gothenburg, Gothenburg, Sweden
- Department of Biology, College of Science and Technology, University of Rwanda, Huye, Rwanda
| | - Myriam Mujawamariya
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
- Department of Biology, College of Science and Technology, University of Rwanda, Huye, Rwanda
| | - Elisée B Ntawuhiganayo
- Department of Biology, College of Science and Technology, University of Rwanda, Huye, Rwanda
- World Agroforestry (ICRAF), Huye, Rwanda
| | - Etienne Zibera
- School of Forestry, Biodiversity and Biological Sciences, College of Agriculture, Animal Sciences and Veterinary Medicine, University of Rwanda, Musanze, Rwanda
| | - Bonaventure Ntirugulirwa
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
- Department of Biology, College of Science and Technology, University of Rwanda, Huye, Rwanda
- Rwanda Agriculture and Animal Resources Development Board, Kigali, Rwanda
| | - Danielle A Way
- Department of Biology, The University of Western Ontario, London, ON, Canada
- Division of Plant Sciences, Research School of Biology, The Australian National University, Canberra, ACT, Australia
- Environmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, USA
- Nicholas School of the Environment, Duke University, Durham, NC, USA
| | - Donat Nsabimana
- School of Forestry, Biodiversity and Biological Sciences, College of Agriculture, Animal Sciences and Veterinary Medicine, University of Rwanda, Musanze, Rwanda
| | - Johan Uddling
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
- Gothenburg Global Biodiversity Centre (GGBC), University of Gothenburg, Gothenburg, Sweden
| | - Göran Wallin
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
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15
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Jalakas P, Takahashi Y, Waadt R, Schroeder JI, Merilo E. Molecular mechanisms of stomatal closure in response to rising vapour pressure deficit. THE NEW PHYTOLOGIST 2021; 232:468-475. [PMID: 34197630 PMCID: PMC8455429 DOI: 10.1111/nph.17592] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2021] [Accepted: 06/28/2021] [Indexed: 05/26/2023]
Abstract
Vapour pressure deficit (VPD), the difference between the saturation and actual air vapour pressures, indicates the level of atmospheric drought and evaporative pressure on plants. VPD increases during climate change due to changes in air temperature and relative humidity. Rising VPD induces stomatal closure to counteract the VPD-mediated evaporative water loss from plants. There are important gaps in our understanding of the molecular VPD-sensing and signalling mechanisms in stomatal guard cells. Here, we discuss recent advances, research directions and open questions with respect to the three components that participate in VPD-induced stomatal closure in Arabidopsis, including: (1) abscisic acid (ABA)-dependent and (2) ABA-independent regulation of the protein kinase OPEN STOMATA 1 (OST1), and (3) the passive hydraulic stomatal response. In the ABA-dependent component, two models are proposed: ABA may be rapidly synthesised or its basal levels may be involved in the stomatal VPD response. Further studies on stomatal VPD signalling should clarify: (1) whether OST1 activation above basal activity is needed for VPD responses, (2) which components are involved in ABA-independent regulation of OST1, (3) the role of other potential OST1 targets in VPD signalling, and (4) to which extent OST1 contributes to stomatal VPD sensitivity in other plant species.
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Affiliation(s)
- Pirko Jalakas
- Institute of Technology, University of Tartu, 50411 Tartu, Estonia
| | - Yohei Takahashi
- Cell and Developmental Biology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0116, USA
| | - Rainer Waadt
- Institute of Technology, University of Tartu, 50411 Tartu, Estonia
| | - Julian I. Schroeder
- Cell and Developmental Biology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0116, USA
| | - Ebe Merilo
- Institute of Technology, University of Tartu, 50411 Tartu, Estonia
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16
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Islam M, Rahman M, Gebrekirstos A, Bräuning A. Tree-ring δ 18O climate signals vary among tree functional types in South Asian tropical moist forests. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 756:143939. [PMID: 33310218 DOI: 10.1016/j.scitotenv.2020.143939] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 11/13/2020] [Accepted: 11/13/2020] [Indexed: 06/12/2023]
Abstract
We present the first annually resolved and statistically reliable tree-ring δ18O (δ18OT) chronologies for the three South Asian tropical moist forest tree species (Chukrasia tabularis A. Juss., Toona ciliata M. Roem., and Lagerstroemia speciosa Roxb.) which differ in their shade tolerance and resistance to water stress. We found significantly higher mean δ18OT values in light-demanding T. ciliata than in intermediate shade tolerant C. tabularis and shade tolerant L. speciosa (p < 0.001). δ18OT in C. tabularis was mainly influenced by pre-monsoon vapor pressure deficit (VPD; r = -0.54, p < 0.01) and post monsoon maximum temperature (Tmax) (r = 0.52, p < 0.01). δ18OT in T. ciliata was strongly negatively correlated with a dry season drought index PDSI (r = -0.65, p < 0.001) and VPD (r = -0.58, p < 0.001). Pre-monsoon Tmax was strongly positively linked with δ18OT in L. speciosa (r = 0.65, p < 0.001), indicating that climatic influences on δ18OT are species-specific and vary among tree functional types. Although there was a week correlation between local precipitation and δ18OT in our studied species, we found a strong correlation between δ18OT and precipitation at a larger spatial scale. Linear mixed effect models revealed that multiple factors improved model performance only in C. tabularis, yielding the best model, which combined VPD and Tmax. The top models in T. ciliata and L. speciosa included only the single factors PDSI and Tmax, highlighting that the way C. tabularis interacts with climate is more complex when compared with other two species. Our analyses suggest that stable oxygen isotope composition in tree rings of South Asian tropical moist forest trees are a suitable proxy of local and regional climate variability and are an important tool for understanding the physiological mechanisms associated with the global hydrological cycle.
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Affiliation(s)
- Mahmuda Islam
- Institute of Geography, Friedrich-Alexander University Erlangen-Nuremberg, Wetterkreuz 15, 91058 Erlangen, Germany; Department of Forestry and Environmental Science, Shahjalal University of Science and Technology, Sylhet 3114, Bangladesh.
| | - Mizanur Rahman
- Institute of Geography, Friedrich-Alexander University Erlangen-Nuremberg, Wetterkreuz 15, 91058 Erlangen, Germany; Department of Forestry and Environmental Science, Shahjalal University of Science and Technology, Sylhet 3114, Bangladesh
| | - Aster Gebrekirstos
- Institute of Geography, Friedrich-Alexander University Erlangen-Nuremberg, Wetterkreuz 15, 91058 Erlangen, Germany; World Agroforestry Centre (ICRAF), United Nations Avenue, P.O. Box 30677-00100, Nairobi, Kenya
| | - Achim Bräuning
- Institute of Geography, Friedrich-Alexander University Erlangen-Nuremberg, Wetterkreuz 15, 91058 Erlangen, Germany
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Zhang Z, Gong J, Li X, Ding Y, Wang B, Shi J, Liu M, Yang B. Underlying mechanism on source-sink carbon balance of grazed perennial grass during regrowth: Insights into optimal grazing regimes of restoration of degraded grasslands in a temperate steppe. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2021; 277:111439. [PMID: 33035939 DOI: 10.1016/j.jenvman.2020.111439] [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: 06/26/2020] [Revised: 08/17/2020] [Accepted: 09/25/2020] [Indexed: 06/11/2023]
Abstract
Overgrazing is the main driver of grassland degradation and productivity reduction in northern China. The restoration of degraded grasslands depends on optimal grazing regimes that modify the source-sink balance to promote best carbon (C) assimilation and allocation, thereby promoting rapid compensatory growth of the grazed plants. We used in situ13CO2 labeling and field regrowth studies of Stipa grandis P.A. Smirn.to examine the effects of different grazing intensities (light, medium, heavy, and grazing exclusion) on photosynthetic C assimilation and partitioning, on reallocation of non-structural carbohydrates during regrowth, and on the underlying regulatory mechanisms. Light grazing increased the sink demand of newly expanded leaves and significantly promoted 13C fixation by increasing the photosynthetic capacity of the leaves and accelerating fructose transfer from the stem. Although C assimilation decreased under medium and heavy grazing, S. grandis exhibited a tolerance strategy that preferentially allocated more starch and 13C to the roots for storage to balance sink competition between newly expanded leaves and the roots. Sucrose phosphate synthase (SPS), sucrose synthase (SS), and other plant hormones regulated source-sink imbalances during regrowth. Abscisic acid promoted accumulation of aboveground biomass by stimulating stem SPS activity, whereas jasmonate increased root starch synthesis, thereby increasing belowground biomass. Overall, S. grandis could optimize source-sink relationships and above- and belowground C allocation to support regrowth after grazing by the regulating activities of SPS, SS and other hormones. These results provide new insights into C budgets under grazing and guidance for sustainable grazing management in semi-arid grasslands.
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Affiliation(s)
- Zihe Zhang
- Key Laboratory of Surface Processes and Resource Ecology, Beijing Key Laboratory of Traditional Chinese Medicine Protection and Utilization, Faculty of Geographical Science, No. 19 Xinjiekouwai Street, Haidian District, Beijing Normal University, Beijing, 100875, China.
| | - Jirui Gong
- Key Laboratory of Surface Processes and Resource Ecology, Beijing Key Laboratory of Traditional Chinese Medicine Protection and Utilization, Faculty of Geographical Science, No. 19 Xinjiekouwai Street, Haidian District, Beijing Normal University, Beijing, 100875, China.
| | - Xiaobing Li
- Key Laboratory of Surface Processes and Resource Ecology, Beijing Key Laboratory of Traditional Chinese Medicine Protection and Utilization, Faculty of Geographical Science, No. 19 Xinjiekouwai Street, Haidian District, Beijing Normal University, Beijing, 100875, China.
| | - Yong Ding
- Grassland Research Institute, Chinese Academy of Agricultural Sciences, 120 Ulanqab East Street, Saihan District, Hohhot, Inner Mongolia, 010021, China.
| | - Biao Wang
- Key Laboratory of Surface Processes and Resource Ecology, Beijing Key Laboratory of Traditional Chinese Medicine Protection and Utilization, Faculty of Geographical Science, No. 19 Xinjiekouwai Street, Haidian District, Beijing Normal University, Beijing, 100875, China.
| | - Jiayu Shi
- Key Laboratory of Surface Processes and Resource Ecology, Beijing Key Laboratory of Traditional Chinese Medicine Protection and Utilization, Faculty of Geographical Science, No. 19 Xinjiekouwai Street, Haidian District, Beijing Normal University, Beijing, 100875, China.
| | - Min Liu
- Key Laboratory of Tourism and Resources Environment, Taishan University, Tai'an, Shandong province, 271021, China.
| | - Bo Yang
- Key Laboratory of Surface Processes and Resource Ecology, Beijing Key Laboratory of Traditional Chinese Medicine Protection and Utilization, Faculty of Geographical Science, No. 19 Xinjiekouwai Street, Haidian District, Beijing Normal University, Beijing, 100875, China.
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18
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Vogado NO, Winter K, Ubierna N, Farquhar GD, Cernusak LA. Directional change in leaf dry matter δ 13C during leaf development is widespread in C3 plants. ANNALS OF BOTANY 2020; 126:981-990. [PMID: 32577724 PMCID: PMC7596372 DOI: 10.1093/aob/mcaa114] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 06/17/2020] [Indexed: 05/23/2023]
Abstract
BACKGROUND AND AIMS The stable carbon isotope ratio of leaf dry matter (δ 13Cp) is generally a reliable recorder of intrinsic water-use efficiency in C3 plants. Here, we investigated a previously reported pattern of developmental change in leaf δ 13Cp during leaf expansion, whereby emerging leaves are initially 13C-enriched compared to mature leaves on the same plant, with their δ 13Cp decreasing during leaf expansion until they eventually take on the δ 13Cp of other mature leaves. METHODS We compiled data to test whether the difference between mature and young leaf δ 13Cp differs between temperate and tropical species, or between deciduous and evergreen species. We also tested whether the developmental change in δ 13Cp is indicative of a concomitant change in intrinsic water-use efficiency. To gain further insight, we made online measurements of 13C discrimination (∆ 13C) in young and mature leaves. KEY RESULTS We found that the δ 13Cp difference between mature and young leaves was significantly larger for deciduous than for evergreen species (-2.1 ‰ vs. -1.4 ‰, respectively). Counter to expectation based on the change in δ 13Cp, intrinsic water-use efficiency did not decrease between young and mature leaves; rather, it did the opposite. The ratio of intercellular to ambient CO2 concentrations (ci/ca) was significantly higher in young than in mature leaves (0.86 vs. 0.72, respectively), corresponding to lower intrinsic water-use efficiency. Accordingly, instantaneous ∆ 13C was also higher in young than in mature leaves. Elevated ci/ca and ∆ 13C in young leaves resulted from a combination of low photosynthetic capacity and high day respiration rates. CONCLUSION The decline in leaf δ 13Cp during leaf expansion appears to reflect the addition of the expanding leaf's own 13C-depleted photosynthetic carbon to that imported from outside the leaf as the leaf develops. This mixing of carbon sources results in an unusual case of isotopic deception: less negative δ 13Cp in young leaves belies their low intrinsic water-use efficiency.
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Affiliation(s)
- Nara O Vogado
- Centre for Tropical Environmental and Sustainability Science, College of Science and Engineering, James Cook University, Cairns, Australia
| | - Klaus Winter
- Smithsonian Tropical Research Institute, Balboa, Ancon, Republic of Panama
| | - Nerea Ubierna
- Research School of Biology, The Australian National University, Canberra, Australia
| | - Graham D Farquhar
- Research School of Biology, The Australian National University, Canberra, Australia
| | - Lucas A Cernusak
- Centre for Tropical Environmental and Sustainability Science, College of Science and Engineering, James Cook University, Cairns, Australia
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19
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Cardoso AA, Brodribb TJ, Kane CN, DaMatta FM, McAdam SAM. Osmotic adjustment and hormonal regulation of stomatal responses to vapour pressure deficit in sunflower. AOB PLANTS 2020; 12:plaa025. [PMID: 32665827 PMCID: PMC7346309 DOI: 10.1093/aobpla/plaa025] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 06/11/2020] [Indexed: 05/14/2023]
Abstract
Dynamic variation of the stomatal pore in response to changes in leaf-air vapour pressure difference (VPD) constitutes a critical regulation of daytime gas exchange. The stomatal response to VPD has been associated with both foliage abscisic acid (ABA) and leaf water potential (Ψ l ); however, causation remains a matter of debate. Here, we seek to separate hydraulic and hormonal control of stomatal aperture by manipulating the osmotic potential of sunflower leaves. In addition, we test whether stomatal responses to VPD in an ABA-deficient mutant (w-1) of sunflower are similar to the wild type. Stomatal apertures during VPD transitions were closely linked with foliage ABA levels in sunflower plants with contrasting osmotic potentials. In addition, we observed that the inability to synthesize ABA at high VPD in w-1 plants was associated with no dynamic or steady-state stomatal response to VPD. These results for sunflower are consistent with a hormonal, ABA-mediated stomatal responses to VPD rather than a hydraulic-driven stomatal response to VPD.
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Affiliation(s)
- Amanda A Cardoso
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania, Australia
- Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil
- Purdue Center for Plant Biology, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, USA
| | - Timothy J Brodribb
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania, Australia
| | - Cade N Kane
- Purdue Center for Plant Biology, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, USA
| | - Fábio M DaMatta
- Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil
| | - Scott A M McAdam
- Purdue Center for Plant Biology, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, USA
- Corresponding author’s e-mail address:
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20
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Baath GS, Rocateli AC, Kakani VG, Singh H, Northup BK, Gowda PH, Katta JR. Growth and physiological responses of three warm-season legumes to water stress. Sci Rep 2020; 10:12233. [PMID: 32699333 PMCID: PMC7376039 DOI: 10.1038/s41598-020-69209-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Accepted: 06/26/2020] [Indexed: 11/09/2022] Open
Abstract
Novel drought-tolerant grain legumes like mothbean (Vigna acontifolia), tepary bean (Phaseolus acutifolius), and guar (Cyamopsis tetragonoloba) may also serve as summer forages, and add resilience to agricultural systems in the Southern Great Plains (SGP). However, limited information on the comparative response of these species to different water regimes prevents identification of the most reliable option. This study was conducted to compare mothbean, tepary bean and guar for their vegetative growth and physiological responses to four different water regimes: 100% (control), and 75%, 50% and 25% of control, applied from 27 to 77 days after planting (DAP). Tepary bean showed the lowest stomatal conductance (gs) and photosynthetic rate (A), but also maintained the highest instantaneous water use efficiency (WUEi) among species at 0.06 and 0.042 m3 m-3 soil moisture levels. Despite maintaining higher A, rates of vegetative growth by guar and mothbean were lower than tepary bean due to their limited leaf sink activity. At final harvest (77 DAP), biomass yield of tepary bean was 38-60% and 41-56% greater than guar and mothbean, respectively, across water deficits. Tepary bean was the most drought-tolerant legume under greenhouse conditions, and hence future research should focus on evaluating this species in extensive production settings.
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Affiliation(s)
- Gurjinder S Baath
- Department of Plant and Soil Sciences, Oklahoma State University, 371 Agricultural Hall, Stillwater, OK, 74078, USA.
| | - Alexandre C Rocateli
- Department of Plant and Soil Sciences, Oklahoma State University, 371 Agricultural Hall, Stillwater, OK, 74078, USA
| | - Vijaya Gopal Kakani
- Department of Plant and Soil Sciences, Oklahoma State University, 371 Agricultural Hall, Stillwater, OK, 74078, USA
| | - Hardeep Singh
- Department of Plant and Soil Sciences, Oklahoma State University, 371 Agricultural Hall, Stillwater, OK, 74078, USA
| | - Brian K Northup
- USDA-ARS, Grazinglands Research Laboratory, 7207 W. Cheyenne St., El Reno, OK, 73036, USA
| | - Prasanna H Gowda
- USDA-ARS, Southeast Area, 114 Experiment Station Road, Stoneville, MS, 38776, USA
| | - Jhansy R Katta
- Department of Plant and Soil Sciences, Oklahoma State University, 371 Agricultural Hall, Stillwater, OK, 74078, USA
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21
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Zhang Z, Gong J, Wang B, Li X, Ding Y, Yang B, Zhu C, Liu M, Zhang W. Regrowth strategies of Leymus chinensis in response to different grazing intensities. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2020; 30:e02113. [PMID: 32112460 DOI: 10.1002/eap.2113] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 01/07/2020] [Accepted: 01/29/2020] [Indexed: 06/10/2023]
Abstract
In temperate grassland ecosystems, grazing can affect plant growth by foraging, trampling, and excretion. The ability of dominant plant species to regrow after grazing is critical, since it allows the regeneration of photosynthetic tissues to support growth. We conducted a field experiment to evaluate the effects of different grazing intensities (control, light, medium, and heavy) on the physiological and biochemical responses of Leymus chinensis and the carbon (C) sources utilized during regrowth. Light grazing promoted regrowth and photoassimilate storage of L. chinensis, by increasing the net photosynthetic rate (Pn ), photosynthetic quenching, light interception, sugar accumulation, sucrose synthase activities, and fructose supply from stems. At medium grazing intensity, L. chinensis had low Pn , light interception, and sugar accumulation, but higher expression of a sucrose transporter gene (LcSUT1) and water-use efficiency, which reflected a tendency to store C in belowground to promote survival. This strategy was associated with regulation by abscisic acid (ABA), jasmonate, and salicylic acid (SA) signaling. However, L. chinensis tolerated heavy grazing by increased ABA and jasmonate-induced promotion of C assimilation and osmotic adjustment, combined with photoprotection against photo-oxidation, suggesting a strategy based on regrowth. In addition, stems were the main C source organs and energy supply rather than roots. Simultaneously, SA represented a weaker defense than ABA and jasmonate. Therefore, L. chinensis adopted different strategies for regrowth under different grazing intensities, and light grazing promoted regrowth the most. Our results demonstrate the regulation of C reserves utilization by phytohormones, and this regulation provides an explanation for recent results about grazing responses.
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Affiliation(s)
- Zihe Zhang
- Key Laboratory of Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing, 100875, China
- Beijing Key Laboratory of Traditional Chinese Medicine Protection and Utilization, Faculty of Geographical Science, Beijing Normal University, Beijing, 100875, China
| | - Jirui Gong
- Key Laboratory of Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing, 100875, China
- Beijing Key Laboratory of Traditional Chinese Medicine Protection and Utilization, Faculty of Geographical Science, Beijing Normal University, Beijing, 100875, China
| | - Biao Wang
- Key Laboratory of Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing, 100875, China
| | - Xiaobing Li
- Key Laboratory of Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing, 100875, China
| | - Yong Ding
- Grassland Research Institute of Chinese Academic of Agricultural Science, Hohhot, Inner Mongolia, 010021, China
| | - Bo Yang
- Key Laboratory of Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing, 100875, China
| | - Chenchen Zhu
- Key Laboratory of Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing, 100875, China
| | - Min Liu
- Key Laboratory of Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing, 100875, China
| | - Wei Zhang
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Sciences, Beijing Normal University, Beijing, 100875, China
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22
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Grossiord C, Buckley TN, Cernusak LA, Novick KA, Poulter B, Siegwolf RTW, Sperry JS, McDowell NG. Plant responses to rising vapor pressure deficit. THE NEW PHYTOLOGIST 2020; 226:1550-1566. [PMID: 32064613 DOI: 10.1111/nph.16485] [Citation(s) in RCA: 327] [Impact Index Per Article: 81.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 02/04/2020] [Indexed: 05/24/2023]
Abstract
Recent decades have been characterized by increasing temperatures worldwide, resulting in an exponential climb in vapor pressure deficit (VPD). VPD has been identified as an increasingly important driver of plant functioning in terrestrial biomes and has been established as a major contributor in recent drought-induced plant mortality independent of other drivers associated with climate change. Despite this, few studies have isolated the physiological response of plant functioning to high VPD, thus limiting our understanding and ability to predict future impacts on terrestrial ecosystems. An abundance of evidence suggests that stomatal conductance declines under high VPD and transpiration increases in most species up until a given VPD threshold, leading to a cascade of subsequent impacts including reduced photosynthesis and growth, and higher risks of carbon starvation and hydraulic failure. Incorporation of photosynthetic and hydraulic traits in 'next-generation' land-surface models has the greatest potential for improved prediction of VPD responses at the plant- and global-scale, and will yield more mechanistic simulations of plant responses to a changing climate. By providing a fully integrated framework and evaluation of the impacts of high VPD on plant function, improvements in forecasting and long-term projections of climate impacts can be made.
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Affiliation(s)
- Charlotte Grossiord
- Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, 8903, Birmensdorf, Switzerland
- École Polytechnique Fédérale de Lausanne EPFL, School of Architecture, Civil and Environmental Engineering ENAC, 1015, Lausanne, Switzerland
| | - Thomas N Buckley
- Department of Plant Sciences, University of California, Davis, Davis, CA, 95616, USA
| | - Lucas A Cernusak
- College of Science and Engineering, James Cook University, Cairns, Qld, 4814, Australia
| | - Kimberly A Novick
- School of Public and Environmental Affairs, Indiana University Bloomington, Bloomington, IN, 47405, USA
| | - Benjamin Poulter
- Biospheric Sciences Lab, NASA Goddard Space Flight Center, Greenbelt, MD, 20771, USA
| | - Rolf T W Siegwolf
- Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, 8903, Birmensdorf, Switzerland
| | - John S Sperry
- Department of Biology, University of Utah, Salt Lake City, UT, 84112, USA
| | - Nate G McDowell
- Earth Systems Science Division, Pacific Northwest National Laboratory, Richland, WA, 99354, USA
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23
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Julkowska MM. Keep it Steamy: Improved Quantification of the Humidity within the Leaf. PLANT PHYSIOLOGY 2019; 181:1396. [PMID: 31767789 PMCID: PMC6878022 DOI: 10.1104/pp.19.01275] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
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24
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Holloway-Phillips M, Cernusak LA, Stuart-Williams H, Ubierna N, Farquhar GD. Two-Source δ 18O Method to Validate the CO 18O-Photosynthetic Discrimination Model: Implications for Mesophyll Conductance. PLANT PHYSIOLOGY 2019; 181:1175-1190. [PMID: 31519787 PMCID: PMC6836848 DOI: 10.1104/pp.19.00633] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Accepted: 09/05/2019] [Indexed: 05/10/2023]
Abstract
Theoretical models of photosynthetic isotopic discrimination of CO2 (13C and 18O) are commonly used to estimate mesophyll conductance (g m). This requires making simplifying assumptions and assigning parameter values so that g m can be solved for as the residual term. Uncertainties in g m estimation occur due to measurement noise and assumptions not holding, including parameter uncertainty and model parametrization. Uncertainties in the 13C model have been explored previously, but there has been little testing undertaken to determine the reliability of g m estimates from the 18O model (g m18). In this study, we exploited the action of carbonic anhydrase in equilibrating CO2 with leaf water and manipulated the observed photosynthetic discrimination (Δ18O) by changing the oxygen isotopic composition of the source gas CO2 and water vapor. We developed a two-source δ18O method, whereby two measurements of Δ18O were obtained for a leaf with its gas-exchange characteristics otherwise unchanged. Measurements were performed in broad bean (Vicia faba) and Algerian oak (Quercus canariensis) in response to light and vapor pressure deficit. Despite manipulating the Δ18O by over 100‰, in most cases we observed consistency in the calculated g m18, providing confidence in the measurements and model theory. Where there were differences in g m18 estimates between source-gas measurements, we explored uncertainty associated with two model assumptions (the isotopic composition of water at the sites of CO2-water exchange, and the humidity of the leaf internal airspace) and found evidence for both. Finally, we provide experimental guidelines to minimize the sensitivity of g m18 estimates to measurement errors. The two-source δ18O method offers a flexible tool for model parameterization and provides an opportunity to refine our understanding of leaf water and CO2 fluxes.
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Affiliation(s)
- Meisha Holloway-Phillips
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory, 2601 Australia
| | - Lucas A Cernusak
- College of Science and Engineering, James Cook University, Cairns, Queensland, 4870 Australia
| | - Hilary Stuart-Williams
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory, 2601 Australia
| | - Nerea Ubierna
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory, 2601 Australia
| | - Graham D Farquhar
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory, 2601 Australia
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