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Leverett A, Kromdijk J. The long and tortuous path towards improving photosynthesis by engineering elevated mesophyll conductance. PLANT, CELL & ENVIRONMENT 2024. [PMID: 38804598 DOI: 10.1111/pce.14940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 03/13/2024] [Accepted: 04/29/2024] [Indexed: 05/29/2024]
Abstract
The growing demand for global food production is likely to be a defining issue facing humanity over the next 50 years. To tackle this challenge, there is a desire to bioengineer crops with higher photosynthetic efficiencies, to increase yields. Recently, there has been a growing interest in engineering leaves with higher mesophyll conductance (gm), which would allow CO2 to move more efficiently from the substomatal cavities to the chloroplast stroma. However, if crop yield gains are to be realised through this approach, it is essential that the methodological limitations associated with estimating gm are fully appreciated. In this review, we summarise these limitations, and outline the uncertainties and assumptions that can affect the final estimation of gm. Furthermore, we critically assess the predicted quantitative effect that elevating gm will have on assimilation rates in crop species. We highlight the need for more theoretical modelling to determine whether altering gm is truly a viable route to improve crop performance. Finally, we offer suggestions to guide future research on gm, which will help mitigate the uncertainty inherently associated with estimating this parameter.
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Affiliation(s)
- Alistair Leverett
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | - Johannes Kromdijk
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
- Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
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2
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Ubierna N, Holloway-Phillips MM, Wingate L, Ogée J, Busch FA, Farquhar GD. Using Carbon Stable Isotopes to Study C 3 and C 4 Photosynthesis: Models and Calculations. Methods Mol Biol 2024; 2790:163-211. [PMID: 38649572 DOI: 10.1007/978-1-0716-3790-6_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/25/2024]
Abstract
Stable carbon isotopes are a powerful tool to study photosynthesis. Initial applications consisted of determining isotope ratios of plant biomass using mass spectrometry. Subsequently, theoretical models relating C isotope values to gas exchange characteristics were introduced and tested against instantaneous online measurements of 13C photosynthetic discrimination. Beginning in the twenty-first century, laser absorption spectroscopes with sufficient precision for determining isotope mixing ratios became commercially available. This has allowed collection of large data sets at lower cost and with unprecedented temporal resolution. More data and accompanying knowledge have permitted refinement of 13C discrimination model equations, but often at the expense of increased model complexity and difficult parametrization. This chapter describes instantaneous online measurements of 13C photosynthetic discrimination, provides recommendations for experimental setup, and presents a thorough compilation of equations available to researchers. We update our previous 2018 version of this chapter by including recently improved descriptions of (photo)respiratory processes and associated fractionations. We discuss the capabilities and limitations of the diverse 13C discrimination model equations and provide guidance for selecting the model complexity needed for different applications.
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Affiliation(s)
- Nerea Ubierna
- Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (INRAE), Unité Mixte de Recherche (UMR)1391 ISPA, Villenave D'Ornon, France
| | - Meisha-Marika Holloway-Phillips
- Research Unit of Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmendsorf, Switzerland
| | - Lisa Wingate
- Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (INRAE), Unité Mixte de Recherche (UMR)1391 ISPA, Villenave D'Ornon, France
| | - Jérôme Ogée
- Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (INRAE), Unité Mixte de Recherche (UMR)1391 ISPA, Villenave D'Ornon, France
| | - Florian A Busch
- School of Biosciences and The Birmingham Institute of Forest Research, University of Birmingham, Birmingham, UK
| | - Graham D Farquhar
- Research School of Biology, Australian National University, Canberra, ACT, Australia
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3
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Smith EN, van Aalst M, Tosens T, Niinemets Ü, Stich B, Morosinotto T, Alboresi A, Erb TJ, Gómez-Coronado PA, Tolleter D, Finazzi G, Curien G, Heinemann M, Ebenhöh O, Hibberd JM, Schlüter U, Sun T, Weber APM. Improving photosynthetic efficiency toward food security: Strategies, advances, and perspectives. MOLECULAR PLANT 2023; 16:1547-1563. [PMID: 37660255 DOI: 10.1016/j.molp.2023.08.017] [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: 07/03/2023] [Revised: 08/20/2023] [Accepted: 08/31/2023] [Indexed: 09/04/2023]
Abstract
Photosynthesis in crops and natural vegetation allows light energy to be converted into chemical energy and thus forms the foundation for almost all terrestrial trophic networks on Earth. The efficiency of photosynthetic energy conversion plays a crucial role in determining the portion of incident solar radiation that can be used to generate plant biomass throughout a growth season. Consequently, alongside the factors such as resource availability, crop management, crop selection, maintenance costs, and intrinsic yield potential, photosynthetic energy use efficiency significantly influences crop yield. Photosynthetic efficiency is relevant to sustainability and food security because it affects water use efficiency, nutrient use efficiency, and land use efficiency. This review focuses specifically on the potential for improvements in photosynthetic efficiency to drive a sustainable increase in crop yields. We discuss bypassing photorespiration, enhancing light use efficiency, harnessing natural variation in photosynthetic parameters for breeding purposes, and adopting new-to-nature approaches that show promise for achieving unprecedented gains in photosynthetic efficiency.
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Affiliation(s)
- Edward N Smith
- Faculty of Science and Engineering, Molecular Systems Biology - Groningen Biomolecular Sciences and Biotechnology, Nijenborgh 4, 9747 AG Groningen, the Netherlands
| | - Marvin van Aalst
- Institute of Quantitative and Theoretical Biology, Cluster of Excellence on Plant Science (CEPLAS), Heinrich Heine University, Universitätsstrasse 1, 40225 Düsseldorf, Germany
| | - Tiina Tosens
- Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, 51006 Tartu, Estonia
| | - Ülo Niinemets
- Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, 51006 Tartu, Estonia
| | - Benjamin Stich
- Institute of Quantitative Genetics and Genomics of Plants, Cluster of Excellence on Plant Science (CEPLAS), Heinrich Heine University, Universitätsstrasse 1, 40225 Düsseldorf, Germany
| | | | | | - Tobias J Erb
- Max Planck Institute for Terrestrial Microbiology, Department of Biochemistry & Synthetic Metabolism, 35043 Marburg, Germany
| | - Paul A Gómez-Coronado
- Max Planck Institute for Terrestrial Microbiology, Department of Biochemistry & Synthetic Metabolism, 35043 Marburg, Germany
| | - Dimitri Tolleter
- Interdisciplinary Research Institute of Grenoble, IRIG-LPCV, Grenoble Alpes University, CNRS, CEA, INRAE, 38000 Grenoble, France
| | - Giovanni Finazzi
- Interdisciplinary Research Institute of Grenoble, IRIG-LPCV, Grenoble Alpes University, CNRS, CEA, INRAE, 38000 Grenoble, France
| | - Gilles Curien
- Interdisciplinary Research Institute of Grenoble, IRIG-LPCV, Grenoble Alpes University, CNRS, CEA, INRAE, 38000 Grenoble, France
| | - Matthias Heinemann
- Faculty of Science and Engineering, Molecular Systems Biology - Groningen Biomolecular Sciences and Biotechnology, Nijenborgh 4, 9747 AG Groningen, the Netherlands
| | - Oliver Ebenhöh
- Institute of Quantitative and Theoretical Biology, Cluster of Excellence on Plant Science (CEPLAS), Heinrich Heine University, Universitätsstrasse 1, 40225 Düsseldorf, Germany
| | - Julian M Hibberd
- Molecular Physiology, Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, UK
| | - Urte Schlüter
- Institute for Plant Biochemistry, Cluster of Excellence on Plant Science (CEPLAS), Heinrich Heine University, Universitätsstrasse 1, 40225 Düsseldorf, Germany
| | - Tianshu Sun
- Molecular Physiology, Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, UK
| | - Andreas P M Weber
- Institute for Plant Biochemistry, Cluster of Excellence on Plant Science (CEPLAS), Heinrich Heine University, Universitätsstrasse 1, 40225 Düsseldorf, Germany.
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4
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Baca Cabrera JC, Hirl RT, Zhu J, Schäufele R, Ogée J, Schnyder H. 18 O enrichment of sucrose and photosynthetic and nonphotosynthetic leaf water in a C 3 grass-atmospheric drivers and physiological relations. PLANT, CELL & ENVIRONMENT 2023. [PMID: 37376738 DOI: 10.1111/pce.14655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 05/19/2023] [Accepted: 06/14/2023] [Indexed: 06/29/2023]
Abstract
The 18 O enrichment (Δ18 O) of leaf water affects the Δ18 O of photosynthetic products such as sucrose, generating an isotopic archive of plant function and past climate. However, uncertainty remains as to whether leaf water compartmentation between photosynthetic and nonphotosynthetic tissue affects the relationship between Δ18 O of bulk leaf water (Δ18 OLW ) and leaf sucrose (Δ18 OSucrose ). We grew Lolium perenne (a C3 grass) in mesocosm-scale, replicated experiments with daytime relative humidity (50% or 75%) and CO2 level (200, 400 or 800 μmol mol-1 ) as factors, and determined Δ18 OLW , Δ18 OSucrose and morphophysiological leaf parameters, including transpiration (Eleaf ), stomatal conductance (gs ) and mesophyll conductance to CO2 (gm ). The Δ18 O of photosynthetic medium water (Δ18 OSSW ) was estimated from Δ18 OSucrose and the equilibrium fractionation between water and carbonyl groups (εbio ). Δ18 OSSW was well predicted by theoretical estimates of leaf water at the evaporative site (Δ18 Oe ) with adjustments that correlated with gas exchange parameters (gs or total conductance to CO2 ). Isotopic mass balance and published work indicated that nonphotosynthetic tissue water was a large fraction (~0.53) of bulk leaf water. Δ18 OLW was a poor proxy for Δ18 OSucrose , mainly due to opposite Δ18 O responses of nonphotosynthetic tissue water (Δ18 Onon-SSW ) relative to Δ18 OSSW , driven by atmospheric conditions.
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Affiliation(s)
- Juan C Baca Cabrera
- Technische Universität München, TUM School of Life Sciences, Lehrstuhl für Grünlandlehre, Freising-Weihenstephan, Germany
- Forschungszentrum Jülich GmbH, Institute of Bio- and Geosciences, Agrosphere (IBG-3), Jülich, Germany
| | - Regina T Hirl
- Technische Universität München, TUM School of Life Sciences, Lehrstuhl für Grünlandlehre, Freising-Weihenstephan, Germany
| | - Jianjun Zhu
- Technische Universität München, TUM School of Life Sciences, Lehrstuhl für Grünlandlehre, Freising-Weihenstephan, Germany
| | - Rudi Schäufele
- Technische Universität München, TUM School of Life Sciences, Lehrstuhl für Grünlandlehre, Freising-Weihenstephan, Germany
| | | | - Hans Schnyder
- Technische Universität München, TUM School of Life Sciences, Lehrstuhl für Grünlandlehre, Freising-Weihenstephan, Germany
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Wang Y, Stutz SS, Bernacchi CJ, Boyd RA, Ort DR, Long SP. Increased bundle-sheath leakiness of CO 2 during photosynthetic induction shows a lack of coordination between the C 4 and C 3 cycles. THE NEW PHYTOLOGIST 2022; 236:1661-1675. [PMID: 36098668 PMCID: PMC9827928 DOI: 10.1111/nph.18485] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Accepted: 08/25/2022] [Indexed: 05/31/2023]
Abstract
Use of a complete dynamic model of NADP-malic enzyme C4 photosynthesis indicated that, during transitions from dark or shade to high light, induction of the C4 pathway was more rapid than that of C3 , resulting in a predicted transient increase in bundle-sheath CO2 leakiness (ϕ). Previously, ϕ has been measured at steady state; here we developed a new method, coupling a tunable diode laser absorption spectroscope with a gas-exchange system to track ϕ in sorghum and maize through the nonsteady-state condition of photosynthetic induction. In both species, ϕ showed a transient increase to > 0.35 before declining to a steady state of 0.2 by 1500 s after illumination. Average ϕ was 60% higher than at steady state over the first 600 s of induction and 30% higher over the first 1500 s. The transient increase in ϕ, which was consistent with model prediction, indicated that capacity to assimilate CO2 into the C3 cycle in the bundle sheath failed to keep pace with the rate of dicarboxylate delivery by the C4 cycle. Because nonsteady-state light conditions are the norm in field canopies, the results suggest that ϕ in these major crops in the field is significantly higher and energy conversion efficiency lower than previous measured values under steady-state conditions.
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Affiliation(s)
- Yu Wang
- The Carl R. Woese Institute for Genomic BiologyUniversity of Illinois Urbana‐Champaign1206 W Gregory DrUrbanaIL61801USA
- DOE Center for Advanced Bioenergy and Bioproducts InnovationUniversity of Illinois at Urbana‐ChampaignUrbanaIL61801USA
| | - Samantha S. Stutz
- The Carl R. Woese Institute for Genomic BiologyUniversity of Illinois Urbana‐Champaign1206 W Gregory DrUrbanaIL61801USA
| | - Carl J. Bernacchi
- DOE Center for Advanced Bioenergy and Bioproducts InnovationUniversity of Illinois at Urbana‐ChampaignUrbanaIL61801USA
- USDA‐ARS Global Change and Photosynthesis Research UnitUniversity of Illinois at Urbana‐ChampaignUrbanaIL61801USA
- Departments of Plant Biology and Crop SciencesUniversity of Illinois at Urbana‐ChampaignUrbanaIL61801USA
| | - Ryan A. Boyd
- The Carl R. Woese Institute for Genomic BiologyUniversity of Illinois Urbana‐Champaign1206 W Gregory DrUrbanaIL61801USA
| | - Donald R. Ort
- The Carl R. Woese Institute for Genomic BiologyUniversity of Illinois Urbana‐Champaign1206 W Gregory DrUrbanaIL61801USA
- DOE Center for Advanced Bioenergy and Bioproducts InnovationUniversity of Illinois at Urbana‐ChampaignUrbanaIL61801USA
- Departments of Plant Biology and Crop SciencesUniversity of Illinois at Urbana‐ChampaignUrbanaIL61801USA
| | - Stephen P. Long
- The Carl R. Woese Institute for Genomic BiologyUniversity of Illinois Urbana‐Champaign1206 W Gregory DrUrbanaIL61801USA
- DOE Center for Advanced Bioenergy and Bioproducts InnovationUniversity of Illinois at Urbana‐ChampaignUrbanaIL61801USA
- Departments of Plant Biology and Crop SciencesUniversity of Illinois at Urbana‐ChampaignUrbanaIL61801USA
- Lancaster Environment CentreLancaster UniversityLancasterLA1 4YQUK
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Chavan SG, Duursma RA, Tausz M, Ghannoum O. Moderate heat stress prevented the observed biomass and yield stimulation caused by elevated CO 2 in two well-watered wheat cultivars. PLANT MOLECULAR BIOLOGY 2022; 110:365-384. [PMID: 35648324 PMCID: PMC9646619 DOI: 10.1007/s11103-022-01276-7] [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: 12/07/2021] [Accepted: 04/21/2022] [Indexed: 05/12/2023]
Abstract
Heat stress (HS) under well-watered conditions was not detrimental to leaf photosynthesis or yield but modified the elevated CO2 response of photosynthesis and yield in two contrasting wheat cultivars. Climate change is increasing the frequency of extreme events such as heat waves, adversely affecting crop productivity. While positive impacts of elevated carbon dioxide (eCO2) on crop productivity are evident, the interactive effects of eCO2 and environmental stresses are still unclear. To investigate the interactive effects of elevated CO2 and heat stress (HS), we grew two contrasting wheat cultivars, early-maturing Scout and high-tillering Yitpi, under non-limiting water and nutrients at ambient (aCO2, 450 ppm) or elevated (eCO2, 650 ppm) CO2 and 22 °C in the glasshouse. Plants were exposed to two 3-day HS cycles at the vegetative (38.1 °C) and/or flowering (33.5 °C) stage. At aCO2, both wheat cultivars showed similar responses of photosynthesis and mesophyll conductance to temperature and produced similar grain yield. Relative to aCO2, eCO2 enhanced photosynthesis rate and reduced stomatal conductance and maximal carboxylation rate (Vcmax). During HS, high temperature stimulated photosynthesis at eCO2 in both cultivars, while eCO2 stimulated photosynthesis in Scout. Electron transport rate (Jmax) was unaffected by any treatment. eCO2 equally enhanced biomass and grain yield of both cultivars in control, but not HS, plants. HS reduced biomass and yield of Scout at eCO2. Yitpi, the cultivar with higher grain nitrogen, underwent a trade-off between grain yield and nitrogen. In conclusion, eCO2 improved photosynthesis of control and HS wheat, and improved biomass and grain yield of control plants only. Under well-watered conditions, HS was not detrimental to photosynthesis or growth but precluded a yield response to eCO2.
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Affiliation(s)
- Sachin G. Chavan
- ARC Centre of Excellence for Translational Photosynthesis, Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751 Australia
| | - Remko A. Duursma
- ARC Centre of Excellence for Translational Photosynthesis, Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751 Australia
| | - Michael Tausz
- Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Dookie, Victoria 3647 Australia
| | - Oula Ghannoum
- ARC Centre of Excellence for Translational Photosynthesis, Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751 Australia
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7
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Wilkes EB, Sessions AL, Zeichner SS, Dallas B, Schubert B, Jahren AH, Eiler JM. Position-specific carbon isotope analysis of serine by gas chromatography/Orbitrap mass spectrometry, and an application to plant metabolism. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2022; 36:e9347. [PMID: 35770334 DOI: 10.1002/rcm.9347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 06/22/2022] [Accepted: 06/23/2022] [Indexed: 06/15/2023]
Abstract
RATIONALE Position-specific 13 C/12 C ratios within amino acids remain largely unexplored in environmental samples due to methodological limitations. We hypothesized that natural-abundance isotope patterns in serine may serve as a proxy for plant metabolic fluxes including photorespiration. Here we describe an Orbitrap method optimized for the position-specific carbon isotope analysis of serine to test our hypothesis and discuss the generalizability of this method to other amino acids. METHODS Position-specific carbon isotope ratios of serine were measured using a Thermo Scientific™ Q Exactive™ GC Orbitrap™. Amino acids were hydrolyzed from Arabidopsis biomass, purified from potential matrix interferences, and derivatized alongside standards. Derivatized serine (N,O-bis(trifluoroacetyl)methyl ester) was isolated using gas chromatography, trapped in a reservoir, and purged into the electron ionization source over tens of minutes, producing fragment ions containing different combinations of atoms from the serine-derivative molecule. The 13 C/12 C ratios of fragments with monoisotopic masses of 110.0217, 138.0166, and 165.0037 Da were monitored in the mass analyzer and used to calculate position-specific δ13 C values relative to a working standard. RESULTS This methodology constrains position-specific δ13 C values for nanomole amounts of serine isolated from chemically complex mixtures. The δ13 C values of fragment ions of serine were characterized with ≤1‰ precisions, leading to propagated standard errors of 0.7-5‰ for each carbon position. Position-specific δ13 C values differed by up to ca 28 ± 5‰ between serine molecules hydrolyzed from plants grown under contrasting pCO2 , selected to promote different fluxes through photosynthesis and photorespiration. The method was validated using pure serine standards characterized offline. CONCLUSIONS This study presents the first Orbitrap-based measurements of natural-abundance, position-specific carbon isotope variation in an amino acid isolated from a biological matrix. We present a method for the precise characterization of isotope ratios in serine and propose applications probing metabolism in plants. We discuss the potential for extending these approaches to other amino acids, paving the way for novel applications.
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Affiliation(s)
- Elise B Wilkes
- Division of Geological and Planetary Sciences, Caltech, Pasadena, CA, USA
| | - Alex L Sessions
- Division of Geological and Planetary Sciences, Caltech, Pasadena, CA, USA
| | - Sarah S Zeichner
- Division of Geological and Planetary Sciences, Caltech, Pasadena, CA, USA
| | - Brooke Dallas
- Division of Geological and Planetary Sciences, Caltech, Pasadena, CA, USA
| | - Brian Schubert
- School of Geosciences, University of Louisiana at Lafayette, Lafayette, LA, USA
| | - A Hope Jahren
- Centre for Earth Evolution and Dynamics, University of Oslo, Oslo, Norway
| | - John M Eiler
- Division of Geological and Planetary Sciences, Caltech, Pasadena, CA, USA
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Momayyezi M, Borsuk AM, Brodersen CR, Gilbert ME, Théroux‐Rancourt G, Kluepfel DA, McElrone AJ. Desiccation of the leaf mesophyll and its implications for CO 2 diffusion and light processing. PLANT, CELL & ENVIRONMENT 2022; 45:1362-1381. [PMID: 35141930 PMCID: PMC9314819 DOI: 10.1111/pce.14287] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 01/18/2022] [Accepted: 01/24/2022] [Indexed: 05/09/2023]
Abstract
Leaves balance CO2 and radiative absorption while maintaining water transport to maximise photosynthesis. Related species with contrasting leaf anatomy can provide insights into inherent and stress-induced links between structure and function for commonly measured leaf traits for important crops. We used two walnut species with contrasting mesophyll anatomy to evaluate these integrated exchange processes under non-stressed and drought conditions using a combination of light microscopy, X-ray microCT, gas exchange, hydraulic conductance, and chlorophyll distribution profiles through leaves. Juglans regia had thicker palisade mesophyll, higher fluorescence in the palisade, and greater low-mesophyll porosity that were associated with greater gas-phase diffusion (gIAS ), stomatal and mesophyll (gm ) conductances and carboxylation capacity. More and highly-packed mesophyll cells and bundle sheath extensions (BSEs) in Juglans microcarpa led to higher fluorescence in the spongy and in proximity to the BSEs. Both species exhibited drought-induced reductions in mesophyll cell volume, yet the associated increases in porosity and gIAS were obscured by declines in biochemical activity that decreased gm . Inherent differences in leaf anatomy between the species were linked to differences in gas exchange, light absorption and photosynthetic capacity, and drought-induced changes in leaf structure impacted performance via imposing species-specific limitations to light absorption, gas exchange and hydraulics.
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Affiliation(s)
- Mina Momayyezi
- Department of Viticulture and EnologyUniversity of CaliforniaDavisCaliforniaUSA
| | - Aleca M. Borsuk
- School of the EnvironmentYale UniversityNew HavenConnecticutUSA
| | | | | | | | | | - Andrew J. McElrone
- Department of Viticulture and EnologyUniversity of CaliforniaDavisCaliforniaUSA
- USDA‐ARSCrops Pathology and Genetics Research UnitDavisCaliforniaUSA
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9
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Jahan E, Thomson PC, Tissue DT. Mesophyll conductance in two cultivars of wheat grown in glacial to super-elevated CO2 concentrations. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:7191-7202. [PMID: 34232298 DOI: 10.1093/jxb/erab320] [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: 04/28/2021] [Accepted: 07/04/2021] [Indexed: 05/26/2023]
Abstract
Mesophyll conductance (gm) is an important factor limiting photosynthesis. However, gm response to long-term growth in variable [CO2] is not well understood, particularly in crop plants. Here, we grew two cultivars of wheat (Halberd and Cranbrook), known to differ in gm under current environmental conditions, in four [CO2] treatments: glacial (206 μmol mol-1), pre-industrial (344 μmol mol-1), current ambient (489 μmol mol-1), and super-elevated (1085 μmol mol-1), and two water treatments (well-watered and moderate water limitation), to develop an evolutionary and future climate perspective on gm control of photosynthesis and water-use efficiency (WUE). In the two wheat genotypes, gm increased with rising [CO2] from glacial to ambient [CO2], but declined at super-elevated [CO2]. The responses of gm to different growth [CO2] also depend on water stress; however, the specific mechanism of gm response to [CO2] remains unclear. Although gm and gm/gsc (mesophyll conductance/stomatal conductance) were strongly associated with the variability of photosynthetic rates (A) and WUE, we found that plants with higher gm may increase A without increasing gsc, which increased WUE. These results may be useful to inform plant breeding programmes and cultivar selection for Australian wheat under future environmental conditions.
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Affiliation(s)
- Eisrat Jahan
- The University of Sydney, School of Life and Environmental Sciences, Camden NSW, Australia
| | - Peter C Thomson
- The University of Sydney, School of Life and Environmental Sciences, Camden NSW, Australia
| | - David T Tissue
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith NSW, Australia
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10
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Jaikumar NS, Stutz SS, Fernandes SB, Leakey ADB, Bernacchi CJ, Brown PJ, Long SP. Can improved canopy light transmission ameliorate loss of photosynthetic efficiency in the shade? An investigation of natural variation in Sorghum bicolor. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:4965-4980. [PMID: 33914063 PMCID: PMC8219039 DOI: 10.1093/jxb/erab176] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Accepted: 04/28/2021] [Indexed: 05/29/2023]
Abstract
Previous studies have found that maximum quantum yield of CO2 assimilation (Φ CO2,max,app) declines in lower canopies of maize and miscanthus, a maladaptive response to self-shading. These observations were limited to single genotypes, leaving it unclear whether the maladaptive shade response is a general property of this C4 grass tribe, the Andropogoneae. We explored the generality of this maladaptation by testing the hypothesis that erect leaf forms (erectophiles), which allow more light into the lower canopy, suffer less of a decline in photosynthetic efficiency than drooping leaf (planophile) forms. On average, Φ CO2,max,app declined 27% in lower canopy leaves across 35 accessions, but the decline was over twice as great in planophiles than in erectophiles. The loss of photosynthetic efficiency involved a decoupling between electron transport and assimilation. This was not associated with increased bundle sheath leakage, based on 13C measurements. In both planophiles and erectophiles, shaded leaves had greater leaf absorptivity and lower activities of key C4 enzymes than sun leaves. The erectophile form is considered more productive because it allows a more effective distribution of light through the canopy to support photosynthesis. We show that in sorghum, it provides a second benefit, maintenance of higher Φ CO2,max,app to support efficient use of that light resource.
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Affiliation(s)
- Nikhil S Jaikumar
- Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Samantha S Stutz
- Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Samuel B Fernandes
- Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Andrew D B Leakey
- Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Carl J Bernacchi
- Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- USDA ARS Global Change and Photosynthesis Research Unit, Urbana, IL 61801, USA
| | - Patrick J Brown
- Department of Plant Sciences, University of California at Davis, Davis, CA 95616, USA
| | - Stephen P Long
- Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- Lancaster Environment Centre, University of Lancaster, Lancaster LA1 4YQ, UK
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Ye J, Chen W, Feng L, Liu G, Wang Y, Li H, Ye Z, Zhang Y. The chaperonin 60 protein SlCpn60α1 modulates photosynthesis and photorespiration in tomato. JOURNAL OF EXPERIMENTAL BOTANY 2020; 71:7224-7240. [PMID: 32915204 DOI: 10.1093/jxb/eraa418] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Accepted: 09/08/2020] [Indexed: 06/11/2023]
Abstract
Photosynthesis, an indispensable biological process of plants, produces organic substances for plant growth, during which photorespiration occurs to oxidize carbohydrates to achieve homeostasis. Although the molecular mechanism underlying photosynthesis and photorespiration has been widely explored, the crosstalk between the two processes remains largely unknown. In this study, we isolated and characterized a T-DNA insertion mutant of tomato (Solanum lycopersicum) named yellow leaf (yl) with yellowish leaves, retarded growth, and chloroplast collapse that hampered both photosynthesis and photorespiration. Genetic and expression analyses demonstrated that the phenotype of yl was caused by a loss-of-function mutation resulting from a single-copy T-DNA insertion in chaperonin 60α1 (SlCPN60α1). SlCPN60α1 showed high expression levels in leaves and was located in both chloroplasts and mitochondria. Silencing of SlCPN60α1using virus-induced gene silencing and RNA interference mimicked the phenotype of yl. Results of two-dimensional electrophoresis and yeast two-hybrid assays suggest that SlCPN60α1 potentially interacts with proteins that are involved in chlorophyll synthesis, photosynthetic electron transport, and the Calvin cycle, and further affect photosynthesis. Moreover, SlCPN60α1 directly interacted with serine hydroxymethyltransferase (SlSHMT1) in mitochondria, thereby regulating photorespiration in tomato. This study outlines the importance of SlCPN60α1 for both photosynthesis and photorespiration, and provides molecular insights towards plant genetic improvement.
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Affiliation(s)
- Jie Ye
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, China
- Boyce Thompson Institute for Plant Research, Cornell University, Ithaca, NY, USA
| | - Weifang Chen
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, China
| | - Longwei Feng
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, China
| | - Genzhong Liu
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, China
| | - Ying Wang
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, China
| | - Hanxia Li
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, China
| | - Zhibiao Ye
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, China
| | - Yuyang Zhang
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, China
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12
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Busch FA, Holloway-Phillips M, Stuart-Williams H, Farquhar GD. Revisiting carbon isotope discrimination in C 3 plants shows respiration rules when photosynthesis is low. NATURE PLANTS 2020; 6:245-258. [PMID: 32170287 DOI: 10.1038/s41477-020-0606-6] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 01/23/2020] [Indexed: 05/12/2023]
Abstract
Stable isotopes are commonly used to study the diffusion of CO2 within photosynthetic plant tissues. The standard method used to interpret the observed preference for the lighter carbon isotope in C3 photosynthesis involves the model of Farquhar et al., which relates carbon isotope discrimination to physical and biochemical processes within the leaf. However, under many conditions the model returns unreasonable results for mesophyll conductance to CO2 diffusion (gm), especially when rates of photosynthesis are low. Here, we re-derive the carbon isotope discrimination model using modified assumptions related to the isotope effect of mitochondrial respiration. In particular, we treat the carbon pool associated with respiration as separate from the pool of primary assimilates. We experimentally test the model by comparing gm values measured with different CO2 source gases varying in their isotopic composition, and show that our new model returns matching gm values that are much more reasonable than those obtained with the previous model. We use our results to discuss CO2 diffusion properties within the mesophyll.
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Affiliation(s)
- Florian A Busch
- Research School of Biology and ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Acton, Australian Capital Territory, Australia.
| | - Meisha Holloway-Phillips
- Research School of Biology and ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Acton, Australian Capital Territory, Australia
- Department of Environmental Sciences, University of Basel, Basel, Switzerland
| | - Hilary Stuart-Williams
- Research School of Biology and ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Acton, Australian Capital Territory, Australia
| | - Graham D Farquhar
- Research School of Biology and ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Acton, Australian Capital Territory, Australia
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13
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Gouveia CSS, Ganança JFT, Slaski J, Lebot V, Pinheiro de Carvalho MÂA. Variation of carbon and isotope natural abundances (δ 15N and δ 13C) of whole-plant sweet potato (Ipomoea batatas L.) subjected to prolonged water stress. JOURNAL OF PLANT PHYSIOLOGY 2019; 243:153052. [PMID: 31689580 DOI: 10.1016/j.jplph.2019.153052] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 07/25/2019] [Accepted: 07/31/2019] [Indexed: 06/10/2023]
Abstract
Sweet potato (Ipomoea batatas L.) is an important crop in the world, cultivated in temperate climates under low inputs. Drought changes the plant biomass allocation, together with the carbon and nitrogen isotopic composition (δ13C and δ15N), whose changes are faintly known in sweet potato crops. Here, we show the biomass allocation of eight sweet potato accessions submitted to drought during 3 months, using the δ13C, δ15N, carbon isotope discrimination (Δ13C), total carbon (TC) and water use efficiency (WUE) traits. The tolerant accessions had improved WUE, with higher TPB and TC. Storage roots and shoots had a heavier δ13C content under drought stress, with greater 13C fixation in roots. The Δ13C did not show a significant association with WUE. The δ15N values indicated a generalised N reallocation between whole-plant organs under drought, as a physiological integrator of response to environmental stress. This information can aid the selection of traits to be used in sweet potato breeding programs, to adapt this crop to climate change.
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Affiliation(s)
- Carla S S Gouveia
- ISOPlexis Genebank, University of Madeira, Campus da Penteada, 9020-105, Funchal, Madeira, Portugal.
| | - José F T Ganança
- ISOPlexis Genebank, University of Madeira, Campus da Penteada, 9020-105, Funchal, Madeira, Portugal
| | - Jan Slaski
- ISOPlexis Genebank, University of Madeira, Campus da Penteada, 9020-105, Funchal, Madeira, Portugal; Ecosystems and Plant Sciences, InnoTech Alberta, PO Bag 4000, Hwy 16A & 75 Street, Vegreville, Alberta, Canada
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14
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Chavan SG, Duursma RA, Tausz M, Ghannoum O. Elevated CO2 alleviates the negative impact of heat stress on wheat physiology but not on grain yield. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:6447-6459. [PMID: 31504692 PMCID: PMC6859723 DOI: 10.1093/jxb/erz386] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 09/06/2019] [Indexed: 05/10/2023]
Abstract
Hot days are becoming hotter and more frequent, threatening wheat yields worldwide. Developing wheat varieties ready for future climates calls for improved understanding of how elevated CO2 (eCO2) and heat stress (HS) interactively impact wheat yields. We grew a modern, high-yielding wheat cultivar (Scout) at ambient CO2 (aCO2, 419 μl l -1) or eCO2 (654 μl l-1) in a glasshouse maintained at 22/15 °C (day/night). Half of the plants were exposed to HS (40/24 °C) for 5 d at anthesis. In non-HS plants, eCO2 enhanced (+36%) CO2 assimilation rates (Asat) measured at growth CO2 despite down-regulation of photosynthetic capacity. HS reduced Asat (-42%) in aCO2- but not in eCO2-grown plants because eCO2 protected photosynthesis by increasing ribulose bisphosphate regeneration capacity and reducing photochemical damage under HS. eCO2 stimulated biomass (+35%) of all plants and grain yield (+30%) of non-HS plants only. Plant biomass initially decreased following HS but recovered at maturity due to late tillering. HS equally reduced grain yield (-40%) in aCO2- and eCO2-grown plants due to grain abortion and reduced grain filling. While eCO2 mitigated the negative impacts of HS at anthesis on wheat photosynthesis and biomass, grain yield was reduced by HS in both CO2 treatments.
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Affiliation(s)
- Sachin G Chavan
- ARC Centre of Excellence for Translational Photosynthesis, Hawkesbury Institute for the Environment, Western Sydney University, Penrith NSW Australia
| | - Remko A Duursma
- ARC Centre of Excellence for Translational Photosynthesis, Hawkesbury Institute for the Environment, Western Sydney University, Penrith NSW Australia
| | - Michael Tausz
- Department of Forest and Ecosystem Science, The University of Melbourne, Creswick, Vic., Australia
| | - Oula Ghannoum
- ARC Centre of Excellence for Translational Photosynthesis, Hawkesbury Institute for the Environment, Western Sydney University, Penrith NSW Australia
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15
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Giuliani R, Karki S, Covshoff S, Lin HC, Coe RA, Koteyeva NK, Evans MA, Quick WP, von Caemmerer S, Furbank RT, Hibberd JM, Edwards GE, Cousins AB. Transgenic maize phosphoenolpyruvate carboxylase alters leaf-atmosphere CO 2 and 13CO 2 exchanges in Oryza sativa. PHOTOSYNTHESIS RESEARCH 2019; 142:153-167. [PMID: 31325077 PMCID: PMC6848035 DOI: 10.1007/s11120-019-00655-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 06/11/2019] [Indexed: 05/07/2023]
Abstract
The engineering process of C4 photosynthesis into C3 plants requires an increased activity of phosphoenolpyruvate carboxylase (PEPC) in the cytosol of leaf mesophyll cells. The literature varies on the physiological effect of transgenic maize (Zea mays) PEPC (ZmPEPC) leaf expression in Oryza sativa (rice). Therefore, to address this issue, leaf-atmosphere CO2 and 13CO2 exchanges were measured, both in the light (at atmospheric O2 partial pressure of 1.84 kPa and at different CO2 levels) and in the dark, in transgenic rice expressing ZmPEPC and wild-type (WT) plants. The in vitro PEPC activity was 25 times higher in the PEPC overexpressing (PEPC-OE) plants (~20% of maize) compared to the negligible activity in WT. In the PEPC-OE plants, the estimated fraction of carboxylation by PEPC (β) was ~6% and leaf net biochemical discrimination against 13CO2[Formula: see text] was ~ 2‰ lower than in WT. However, there were no differences in leaf net CO2 assimilation rates (A) between genotypes, while the leaf dark respiration rates (Rd) over three hours after light-dark transition were enhanced (~ 30%) and with a higher 13C composition [Formula: see text] in the PEPC-OE plants compared to WT. These data indicate that ZmPEPC in the PEPC-OE rice plants contributes to leaf carbon metabolism in both the light and in the dark. However, there are some factors, potentially posttranslational regulation and PEP availability, which reduce ZmPEPC activity in vivo.
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Affiliation(s)
- Rita Giuliani
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-4236, USA
| | - Shanta Karki
- C4 Rice Center, International Rice Research Institute (IRRI), Los Baños, Philippines
| | - Sarah Covshoff
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
| | - Hsiang-Chun Lin
- C4 Rice Center, International Rice Research Institute (IRRI), Los Baños, Philippines
| | - Robert A Coe
- C4 Rice Center, International Rice Research Institute (IRRI), Los Baños, Philippines
| | - Nuria K Koteyeva
- Laboratory of Anatomy and Morphology, V.L. Komarov Botanical Institute of the Russian Academy of Sciences, Prof. Popov Street 2, St. Petersburg, Russia, 197376
| | - Marc A Evans
- Department of Mathematics and Statistics, Washington State University, Pullman, WA, 99164-3113, USA
| | - W Paul Quick
- C4 Rice Center, International Rice Research Institute (IRRI), Los Baños, Philippines
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2TN, UK
| | - Susanne von Caemmerer
- Division of Plant Sciences, Research School of Biology, The Australian National University, Canberra, ACT, 0200, Australia
| | - Robert T Furbank
- Division of Plant Sciences, Research School of Biology, The Australian National University, Canberra, ACT, 0200, Australia
| | - Julian M Hibberd
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
| | - Gerald E Edwards
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-4236, USA
| | - Asaph B Cousins
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-4236, USA.
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16
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Mizokami Y, Sugiura D, Watanabe CKA, Betsuyaku E, Inada N, Terashima I. Elevated CO2-induced changes in mesophyll conductance and anatomical traits in wild type and carbohydrate-metabolism mutants of Arabidopsis. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:4807-4818. [PMID: 31056658 PMCID: PMC6760322 DOI: 10.1093/jxb/erz208] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2018] [Accepted: 04/25/2019] [Indexed: 05/23/2023]
Abstract
Decreases in photosynthetic rate, stomatal conductance (gs), and mesophyll conductance (gm) are often observed under elevated CO2 conditions. However, which anatomical and/or physiological factors contribute to the decrease in gm is not fully understood. Arabidopsis thaliana wild-type and carbon-metabolism mutants (gwd1, pgm1, and cfbp1) with different accumulation patterns of non-structural carbohydrates were grown at ambient (400 ppm) and elevated (800 ppm) CO2. Anatomical and physiological traits of leaves were measured to investigate factors causing the changes in gm and in the mesophyll resistance (expressed as the reciprocal of mesophyll conductance per unit chloroplast surface area facing to intercellular space, Sc/gm). When grown at elevated CO2, all the lines showed increases in cell wall mass, cell wall thickness, and starch content, but not in leaf thickness. gm measured at 800 ppm CO2 was significantly lower than at 400 ppm CO2 in all the lines. Changes in Sc/gm were associated with thicker cell walls rather than with excess starch content. The results indicate that the changes in gm and Sc/gm that occur in response to elevated CO2 are independent of non-structural carbohydrates, and the cell wall represents a greater limitation factor for gm than starch.
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Affiliation(s)
- Yusuke Mizokami
- Commissariat à l’Energie Atomique et aux Energies Alternatives, Centre National de la Recherche Scientifique, UMR 7265 Biologie Végétale et Microbiologie Environnementale, Aix Marseille Université, Saint-Paul-lez-Durance, France
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, Japan
| | - Daisuke Sugiura
- Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, Japan
| | - Chihiro K A Watanabe
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, Japan
| | - Eriko Betsuyaku
- Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan
| | - Noriko Inada
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka, Japan
| | - Ichiro Terashima
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, Japan
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17
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Ubierna N, Cernusak LA, Holloway-Phillips M, Busch FA, Cousins AB, Farquhar GD. Critical review: incorporating the arrangement of mitochondria and chloroplasts into models of photosynthesis and carbon isotope discrimination. PHOTOSYNTHESIS RESEARCH 2019; 141:5-31. [PMID: 30955143 DOI: 10.1007/s11120-019-00635-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2018] [Accepted: 03/07/2019] [Indexed: 06/09/2023]
Abstract
The arrangement of mitochondria and chloroplasts, together with the relative resistances of cell wall and chloroplast, determine the path of diffusion out of the leaf for (photo)respired CO2. Traditional photosynthesis models have assumed a tight arrangement of chloroplasts packed together against the cell wall with mitochondria located behind the chloroplasts, deep inside the cytosol. Accordingly, all (photo)respired CO2 must cross the chloroplast before diffusing out of the leaf. Different arrangements have recently been considered, where all or part of the (photo)respired CO2 diffuses through the cytosol without ever entering the chloroplast. Assumptions about the path for the (photo)respiratory flux are particularly relevant for the calculation of mesophyll conductance (gm). If (photo)respired CO2 can diffuse elsewhere besides the chloroplast, apparent gm is no longer a mere physical resistance but a flux-weighted variable sensitive to the ratio of (photo)respiration to net CO2 assimilation. We discuss existing photosynthesis models in conjunction with their treatment of the (photo)respiratory flux and present new equations applicable to the generalized case where (photo)respired CO2 can diffuse both into the chloroplast and through the cytosol. Additionally, we present a new generalized Δ13C model that incorporates this dual diffusion pathway. We assess how assumptions about the fate of (photo)respired CO2 affect the interpretation of photosynthetic data and the challenges it poses for the application of different models.
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Affiliation(s)
- Nerea Ubierna
- Research School of Biology, Australian National University, Acton, ACT, 2601, Australia.
| | - Lucas A Cernusak
- College of Science and Engineering, James Cook University, Cairns, QLD, Australia
| | | | - Florian A Busch
- Research School of Biology, Australian National University, Acton, ACT, 2601, Australia
| | - Asaph B Cousins
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-4236, USA
| | - Graham D Farquhar
- Research School of Biology, Australian National University, Acton, ACT, 2601, Australia
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18
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Giuliani R, Karki S, Covshoff S, Lin HC, Coe RA, Koteyeva NK, Quick WP, Von Caemmerer S, Furbank RT, Hibberd JM, Edwards GE, Cousins AB. Knockdown of glycine decarboxylase complex alters photorespiratory carbon isotope fractionation in Oryza sativa leaves. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:2773-2786. [PMID: 30840760 PMCID: PMC6506765 DOI: 10.1093/jxb/erz083] [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: 10/23/2018] [Accepted: 02/12/2019] [Indexed: 05/07/2023]
Abstract
The influence of reduced glycine decarboxylase complex (GDC) activity on leaf atmosphere CO2 and 13CO2 exchange was tested in transgenic Oryza sativa with the GDC H-subunit knocked down in leaf mesophyll cells. Leaf measurements on transgenic gdch knockdown and wild-type plants were carried out in the light under photorespiratory and low photorespiratory conditions (i.e. 18.4 kPa and 1.84 kPa atmospheric O2 partial pressure, respectively), and in the dark. Under approximately current ambient O2 partial pressure (18.4 kPa pO2), the gdch knockdown plants showed an expected photorespiratory-deficient phenotype, with lower leaf net CO2 assimilation rates (A) than the wild-type. Additionally, under these conditions, the gdch knockdown plants had greater leaf net discrimination against 13CO2 (Δo) than the wild-type. This difference in Δo was in part due to lower 13C photorespiratory fractionation (f) ascribed to alternative decarboxylation of photorespiratory intermediates. Furthermore, the leaf dark respiration rate (Rd) was enhanced and the 13CO2 composition of respired CO2 (δ13CRd) showed a tendency to be more depleted in the gdch knockdown plants. These changes in Rd and δ13CRd were due to the amount and carbon isotopic composition of substrates available for dark respiration. These results demonstrate that impairment of the photorespiratory pathway affects leaf 13CO2 exchange, particularly the 13C decarboxylation fractionation associated with photorespiration.
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Affiliation(s)
- Rita Giuliani
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, USA
| | - Shanta Karki
- C4 Rice Center, International Rice Research Institute (IRRI), Los Baños, Philippines
| | - Sarah Covshoff
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | - Hsiang-Chun Lin
- C4 Rice Center, International Rice Research Institute (IRRI), Los Baños, Philippines
| | - Robert A Coe
- C4 Rice Center, International Rice Research Institute (IRRI), Los Baños, Philippines
| | - Nuria K Koteyeva
- Laboratory of Anatomy and Morphology, V.L. Komarov Botanical Institute of the Russian Academy of Sciences, St. Petersburg, Russia
| | - W Paul Quick
- C4 Rice Center, International Rice Research Institute (IRRI), Los Baños, Philippines
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK
| | - Susanne Von Caemmerer
- Division of Plant Sciences, Research School of Biology, The Australian National University, Canberra, Australia
| | - Robert T Furbank
- Division of Plant Sciences, Research School of Biology, The Australian National University, Canberra, Australia
| | - Julian M Hibberd
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | - Gerald E Edwards
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, USA
| | - Asaph B Cousins
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, USA
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19
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Mizokami Y, Noguchi K, Kojima M, Sakakibara H, Terashima I. Effects of instantaneous and growth CO 2 levels and abscisic acid on stomatal and mesophyll conductances. PLANT, CELL & ENVIRONMENT 2019; 42:1257-1269. [PMID: 30468514 DOI: 10.1111/pce.13484] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 11/08/2018] [Accepted: 11/10/2018] [Indexed: 05/26/2023]
Abstract
C3 photosynthesis is often limited by CO2 diffusivity or stomatal (gs ) and mesophyll (gm ) conductances. To characterize effects of stomatal closure induced by either high CO2 or abscisic acid (ABA) application on gm , we examined gs and gm in the wild type (Col-0) and ost1 and slac1-2 mutants of Arabidopsis thaliana grown at 390 or 780 μmol mol-1 CO2 . Stomata of these mutants were reported to be insensitive to both high CO2 and ABA. When the ambient CO2 increased instantaneously, gm decreased in all these plants, whereas gs in ost1 and slac1-2 was unchanged. Therefore, the decrease in gm in response to high CO2 occurred irrespective of the responses of gs . gm was mainly determined by the instantaneous CO2 concentration during the measurement and not markedly by the CO2 concentration during the growth. Exogenous application of ABA to Col-0 caused the decrease in the intercellular CO2 concentration (Ci ). With the decrease in Ci , gm did not increase but decreased, indicating that the response of gm to CO2 and that to ABA are differently regulated and that ABA content in the leaves plays an important role in the regulation of gm .
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Affiliation(s)
- Yusuke Mizokami
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
| | - Ko Noguchi
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Japan
| | - Mikiko Kojima
- Plant Productivity Systems Research Group, RIKEN Center for Sustainable Resource Science, Yokohama, Japan
| | - Hitoshi Sakakibara
- Plant Productivity Systems Research Group, RIKEN Center for Sustainable Resource Science, Yokohama, Japan
| | - Ichiro Terashima
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
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20
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Gouveia CSS, Ganança JFT, Slaski J, Lebot V, Pinheiro de Carvalho MÂA. Stable isotope natural abundances (δ 13C and δ 15N) and carbon-water relations as drought stress mechanism response of taro (Colocasia esculenta L. Schott). JOURNAL OF PLANT PHYSIOLOGY 2019; 232:100-106. [PMID: 30537596 DOI: 10.1016/j.jplph.2018.11.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 11/21/2018] [Accepted: 11/26/2018] [Indexed: 06/09/2023]
Abstract
Taro (Colocasia esculenta L. Schott) is an important staple food crop in tropical and developing countries, having high water requirements. The purpose of this study was to evaluate the feasibility of using carbon and nitrogen isotopic composition (δ13C and δ15N) as a physiological indicator of taro response to drought, and elucidation of the relationship between the water use efficiency (WUE) under drought conditions and carbon isotope discrimination (Δ13C). As an alternative to WUE determination, obtained by measuring plant growth and water loss during an entire vegetative cycle, we have used Δ13C to determine the tolerance of C3 taro plants to drought. Seven taro accessions from Madeira, Canary Islands and the Secretariat of the Pacific Community (Fiji) collections were grown under greenhouse conditions and subjected to different watering regimes during a one-year cycle. Total plant biomass (TPB), WUE and δ15N were determined at the whole-plant level (WP). Corms and shoots were evaluated separately for nitrogen content (N), δ13C, Δ13C and δ15N. WUE showed positive correlation with TPB (r = 0.4) and negative with Δ13C (r = -0.3); Corm δ15N showed positive correlations with WP δ15N (r = 0.6) and corm N (r = 0.3). Accordingly, the taro plants with enhanced WUE exhibited low Δ13C and δ15N values as a physiological response to drought stress. The approach used in the present study has developed new tools that could be used in further research on taro response to environmental stresses.
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Affiliation(s)
- Carla S S Gouveia
- ISOPlexis Genebank, University of Madeira, Campus da Penteada, 9020-105, Funchal, Madeira, Portugal.
| | - José F T Ganança
- ISOPlexis Genebank, University of Madeira, Campus da Penteada, 9020-105, Funchal, Madeira, Portugal
| | - Jan Slaski
- ISOPlexis Genebank, University of Madeira, Campus da Penteada, 9020-105, Funchal, Madeira, Portugal; Ecosystems and Plant Sciences, InnoTech Alberta, PO Bag 4000, Hwy 16A & 75 Street, Vegreville, Alberta, Canada
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21
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Gong XY, Tcherkez G, Wenig J, Schäufele R, Schnyder H. Determination of leaf respiration in the light: comparison between an isotopic disequilibrium method and the Laisk method. THE NEW PHYTOLOGIST 2018; 218:1371-1382. [PMID: 29611899 DOI: 10.1111/nph.15126] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Accepted: 02/16/2018] [Indexed: 06/08/2023]
Abstract
Quantification of leaf respiration is important for understanding plant physiology and ecosystem biogeochemical processes. Leaf respiration continues in the light (RL ) but supposedly at a lower rate than in the dark (RDk ). However, there is no method for direct measurement of RL and the available methods require nonphysiological measurement conditions. A method based on isotopic disequilibrium quantified RL (RL13C ) and mesophyll conductance of young and old fully expanded leaves of six species. RL13C was compared to RL determined by the Laisk method (RL Laisk ) on the very same leaves with a minimum time lag. RL 13C and RL Laisk were generally lower than RDk , and were not significantly affected by leaf ageing. RL Laisk and RL 13C were positively correlated (r2 = 0.35), and both were positively correlated with RDk (r2 ≥ 0.6). RL Laisk was systematically lower than RL 13C by 0.4 μmol m-2 s-1 . Using A/Cc instead of A/Ci curves, a higher photocompensation point Γ* (by 5 μmol mol-1 ) was found but no influence on RL Laisk estimates was observed. The results imply that the Laisk method underestimates actual RL significantly, probably related to the measurement condition of low CO2 and irradiance. The isotopic disequilibrium method is useful for assessing responses of RL to irradiance and CO2 , improving our mechanistic understanding of RL .
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Affiliation(s)
- Xiao Ying Gong
- Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising, Germany
- Department of Ecology, College of Natural Resources and Environment, South China Agricultural University, Guangzhou, 510642, China
| | - Guillaume Tcherkez
- Research School of Biology, ANU College of Medicine, Biology and Environment, Australian National University, Canberra, ACT, 0200, Australia
| | - Johannes Wenig
- Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising, Germany
| | - Rudi Schäufele
- Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising, Germany
| | - Hans Schnyder
- Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising, Germany
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22
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Flexas J, Cano FJ, Carriquí M, Coopman RE, Mizokami Y, Tholen D, Xiong D. CO2 Diffusion Inside Photosynthetic Organs. THE LEAF: A PLATFORM FOR PERFORMING PHOTOSYNTHESIS 2018. [DOI: 10.1007/978-3-319-93594-2_7] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Ubierna N, Holloway-Phillips MM, Farquhar GD. Using Stable Carbon Isotopes to Study C 3 and C 4 Photosynthesis: Models and Calculations. Methods Mol Biol 2018; 1770:155-196. [PMID: 29978402 DOI: 10.1007/978-1-4939-7786-4_10] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Stable carbon isotopes are a powerful tool to study photosynthesis. Initial applications consisted of determining isotope ratios of plant biomass using mass spectrometry. Subsequently, theoretical models relating C-isotope values to gas exchange characteristics were introduced and tested against instantaneous online measurements of 13C photosynthetic discrimination. Beginning in the twenty-first century, tunable diode laser spectroscopes with sufficient precision for determining isotope mixing ratios became commercially available. This has allowed collection of large data sets, at low cost and with unprecedented temporal resolution. With more data and accompanying knowledge, it has become apparent that there is a need for increased complexity in models and calculations. This chapter describes instantaneous online measurements of 13C photosynthetic discrimination, provides recommendations for experimental setup, and presents a thorough compilation of equations needed for different applications.
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Affiliation(s)
- Nerea Ubierna
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, USA.
| | | | - Graham D Farquhar
- Research School of Biology, Australian National University, Canberra, ACT, Australia
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Ubierna N, Gandin A, Boyd RA, Cousins AB. Temperature response of mesophyll conductance in three C 4 species calculated with two methods: 18 O discrimination and in vitro V pmax. THE NEW PHYTOLOGIST 2017; 214:66-80. [PMID: 27918624 DOI: 10.1111/nph.14359] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 10/27/2016] [Indexed: 05/08/2023]
Abstract
Mesophyll conductance (gm ) is an important factor limiting rates of C3 photosynthesis. However, its role in C4 photosynthesis is poorly understood because it has been historically difficult to estimate. We use two methods to derive the temperature responses of gm in C4 species. The first (Δ18 O) combines measurements of gas exchange with models and measurements of 18 O discrimination. The second method (in vitro Vpmax ) derives gm by retrofitting models of C4 photosynthesis and 13 C discrimination with gas exchange, kinetic constants and in vitro Vpmax measurements. The two methods produced similar gm for Setaria viridis and Zea mays. Additionally, we present the first temperature response (10-40°C) of C4 gm in S. viridis, Z. mays and Miscanthus × giganteus. Values for gm at 25°C ranged from 2.90 to 7.85 μmol m-2 s-1 Pa-1 . Our study demonstrated that: the two described methods are suitable to calculate gm in C4 species; gm values in C4 are similar to high-end values reported for C3 species; and gm increases with temperature analogous to reports for C3 species and the response is species specific. These results improve our mechanistic understanding of C4 photosynthesis.
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Affiliation(s)
- Nerea Ubierna
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-4236, USA
| | - Anthony Gandin
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-4236, USA
| | - Ryan A Boyd
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-4236, USA
| | - Asaph B Cousins
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-4236, USA
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25
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Momayyezi M, Guy RD. Substantial role for carbonic anhydrase in latitudinal variation in mesophyll conductance of Populus trichocarpa Torr. & Gray. PLANT, CELL & ENVIRONMENT 2017; 40:138-149. [PMID: 27761902 DOI: 10.1111/pce.12851] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Revised: 10/14/2016] [Accepted: 10/16/2016] [Indexed: 06/06/2023]
Abstract
In Populus trichocarpa (black cottonwood), net photosynthesis (An ) varies with latitude and, in northern genotypes, is supported by higher stomatal conductance (gs ). We report here a parallel cline in mesophyll conductance (gm ) and link this variation to carbonic anhydrase (CA) activity. Using concurrent carbon isotope discrimination and chlorophyll fluorescence methods, we examined the effects of acetazolamide, an inhibitor of CA, on gm in six representative genotypes (three from either end of the north-south cline). Acetazolamide reduced CA activity, gm , gs , chloroplast CO2 concentration (Cc ) and An at normal CO2 (400 μmol mol-1 ), the latter being reversible at saturating CO2 . Absolute reductions in An , gm and CA activity were greater in northern genotypes than in southern genotypes (P < 0.025) but percent reductions were similar. In contrast, northern genotypes showed lower percent reduction in Cc compared to southern genotypes (P < 0.025). The northern genotypes had greater CA activity relative to both leaf area (two-fold) and mass (1.8-fold) (P < 0.016). The relationship between CA activity and gm was similar whether the variation was inherent or inhibitor induced. We suggest that greater CA activity contributes to higher gm in northern P. trichocarpa genotypes, but other diffusion pathway components may also be involved.
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Affiliation(s)
- Mina Momayyezi
- Department of Forest and Conservation Sciences, Faculty of Forestry, University of British Columbia, Forest Sciences Centre, 2424 Main Mall, Vancouver, British Columbia, V6T 1Z4, Canada
| | - Robert D Guy
- Department of Forest and Conservation Sciences, Faculty of Forestry, University of British Columbia, Forest Sciences Centre, 2424 Main Mall, Vancouver, British Columbia, V6T 1Z4, Canada
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26
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Gong XY, Schäufele R, Schnyder H. Bundle-sheath leakiness and intrinsic water use efficiency of a perennial C4 grass are increased at high vapour pressure deficit during growth. JOURNAL OF EXPERIMENTAL BOTANY 2017; 68:321-333. [PMID: 27864539 PMCID: PMC5853292 DOI: 10.1093/jxb/erw417] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 10/20/2016] [Indexed: 05/05/2023]
Abstract
Bundle-sheath leakiness (ϕ) is a key parameter of the CO2-concentrating mechanism of C4 photosynthesis and is related to leaf-level intrinsic water use efficiency (WUEi). This work studied short-term dynamic responses of ϕ to alterations of atmospheric CO2 concentration in Cleistogenes squarrosa, a perennial grass, grown at high (1.6 kPa) or low (0.6 kPa) vapour pressure deficit (VPD) combined with high or low N supply in controlled environment experiments. ϕ was determined by concurrent measurements of photosynthetic gas exchange and on-line carbon isotope discrimination, using a new protocol. Growth at high VPD led to an increase of ϕ by 0.13 and a concurrent increase of WUEi by 14%, with similar effects at both N levels. ϕ responded dynamically to intercellular CO2 concentration (C i), increasing with C i Across treatments, ϕ was negatively correlated to the ratio of CO2 saturated assimilation rate to carboxylation efficiency (a proxy of the relative activities of Rubisco and phosphoenolpyruvate carboxylase) indicating that the long-term environmental effect on ϕ was related to the balance between C3 and C4 cycles. Our study revealed considerable dynamic and long-term variation in ϕ of C. squarrosa, suggesting that ϕ should be determined when carbon isotope discrimination is used to assess WUEi Also, the data indicate a trade-off between WUEi and energetic efficiency in C. squarrosa.
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Affiliation(s)
- Xiao Ying Gong
- Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354 Freising, Germany
| | - Rudi Schäufele
- Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354 Freising, Germany
| | - Hans Schnyder
- Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354 Freising, Germany
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27
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Jansen-Willems AB, Lanigan GJ, Grünhage L, Müller C. Carbon cycling in temperate grassland under elevated temperature. Ecol Evol 2016; 6:7856-7868. [PMID: 30128135 PMCID: PMC6093167 DOI: 10.1002/ece3.2210] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 05/02/2016] [Accepted: 05/09/2016] [Indexed: 11/21/2022] Open
Abstract
An increase in mean soil surface temperature has been observed over the last century, and it is predicted to further increase in the future. The effect of increased temperature on ecosystem carbon fluxes in a permanent temperate grassland was studied in a long‐term (6 years) field experiment, using multiple temperature increments induced by IR lamps. Ecosystem respiration (R‐eco) and net ecosystem exchange (NEE) were measured and modeled by a modified Lloyd and Taylor model including a soil moisture component for R‐eco (average R2 of 0.78) and inclusion of a photosynthetic component based on temperature and radiation for NEE (R2 = 0.65). Modeled NEE values ranged between 2.3 and 5.3 kg CO2 m−2 year−1, depending on treatment. An increase of 2 or 3°C led to increased carbon losses, lowering the carbon storage potential by around 4 tonnes of C ha−1 year−1. The majority of significant NEE differences were found during night‐time compared to daytime. This suggests that during daytime the increased respiration could be offset by an increase in photosynthetic uptake. This was also supported by differences in δ13C and δ18O, indicating prolonged increased photosynthetic activity associated with the higher temperature treatments. However, this increase in photosynthesis was insufficient to counteract the 24 h increase in respiration, explaining the higher CO2 emissions due to elevated temperature.
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Affiliation(s)
- Anne B Jansen-Willems
- Teagasc Johnstown Castle Wexford, Co. Wexford Ireland.,Department of Experimental Plant Ecology (IFZ) JLU Giessen Heinrich-Buff-Ring 26-32 35390 Giessen Germany
| | | | - Ludger Grünhage
- Department of Experimental Plant Ecology (IFZ) JLU Giessen Heinrich-Buff-Ring 26-32 35390 Giessen Germany
| | - Christoph Müller
- Department of Experimental Plant Ecology (IFZ) JLU Giessen Heinrich-Buff-Ring 26-32 35390 Giessen Germany.,School of Biology and Environmental Science University College Dublin Dublin Ireland
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Ghashghaie J, Badeck FW, Girardin C, Huignard C, Aydinlis Z, Fonteny C, Priault P, Fresneau C, Lamothe-Sibold M, Streb P, Terwilliger VJ. Changes and their possible causes in δ13C of dark-respired CO2 and its putative bulk and soluble sources during maize ontogeny. JOURNAL OF EXPERIMENTAL BOTANY 2016; 67:2603-15. [PMID: 26970389 DOI: 10.1093/jxb/erw075] [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] [Indexed: 05/28/2023]
Abstract
The issues of whether, where, and to what extent carbon isotopic fractionations occur during respiration affect interpretations of plant functions that are important to many disciplines across the natural sciences. Studies of carbon isotopic fractionation during dark respiration in C3 plants have repeatedly shown respired CO2 to be (13)C enriched relative to its bulk leaf sources and (13)C depleted relative to its bulk root sources. Furthermore, two studies showed respired CO2 to become progressively (13)C enriched during leaf ontogeny and (13)C depleted during root ontogeny in C3 legumes. As such data on C4 plants are scarce and contradictory, we investigated apparent respiratory fractionations of carbon and their possible causes in different organs of maize plants during early ontogeny. As in the C3 plants, leaf-respired CO2 was (13)C enriched whereas root-respired CO2 was (13)C depleted relative to their putative sources. In contrast to the findings for C3 plants, however, not only root- but also leaf-respired CO2 became more (13)C depleted during ontogeny. Leaf-respired CO2 was highly (13)C enriched just after light-dark transition but the enrichment rapidly decreased over time in darkness. We conclude that (i) although carbon isotopic fractionations in C4 maize and leguminous C3 crop roots are similar, increasing phosphoenolpyruvate-carboxylase activity during maize ontogeny could have produced the contrast between the progressive (13)C depletion of maize leaf-respired CO2 and (13)C enrichment of C3 leaf-respired CO2 over time, and (ii) in both maize and C3 leaves, highly (13)C enriched leaf-respired CO2 at light-to-dark transition and its rapid decrease during darkness, together with the observed decrease in leaf malate content, may be the result of a transient effect of light-enhanced dark respiration.
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Affiliation(s)
- Jaleh Ghashghaie
- Ecologie Systématique Evolution, Université Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91400 Orsay, France
| | - Franz W Badeck
- Genomics Research Centre, Council for Agricultural Research and Economics, 29017 Fiorenzuola d'Arda (PC), Italy
| | - Cyril Girardin
- UMR ECOSYS, INRA, AgroParisTech, Université Paris-Saclay, 78850 Thiverval-Grignon, France
| | - Christophe Huignard
- Ecologie Systématique Evolution, Université Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91400 Orsay, France
| | - Zackarie Aydinlis
- Ecologie Systématique Evolution, Université Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91400 Orsay, France
| | - Charlotte Fonteny
- Ecologie Systématique Evolution, Université Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91400 Orsay, France
| | - Pierrick Priault
- Université de Lorraine, UMR Ecologie et Ecophysiologie Forestière, 54506 Vandoeuvre-lès-Nancy, France INRA, UMR Ecologie et Ecophysiologie Forestière, 54280 Champenoux, France
| | - Chantal Fresneau
- Ecologie Systématique Evolution, Université Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91400 Orsay, France
| | - Marlène Lamothe-Sibold
- Institute of Plant Sciences Paris-Saclay, IPS2, CNRS, INRA, Université Paris-Sud, Université Evry, Université Paris-Saclay, 91405 Orsay, France
| | - Peter Streb
- Ecologie Systématique Evolution, Université Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91400 Orsay, France
| | - Valery J Terwilliger
- Department of Geography, 1475 Jayhawk Drive, University of Kansas, Lawrence, KS 66045, USA School of Natural Sciences, 5200 North Lake Road, University of California, CA 95343, USA
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29
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Lamade E, Tcherkez G, Darlan NH, Rodrigues RL, Fresneau C, Mauve C, Lamothe-Sibold M, Sketriené D, Ghashghaie J. Natural (13) C distribution in oil palm (Elaeis guineensis Jacq.) and consequences for allocation pattern. PLANT, CELL & ENVIRONMENT 2016; 39:199-212. [PMID: 26228944 DOI: 10.1111/pce.12606] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 06/26/2015] [Indexed: 06/04/2023]
Abstract
Oil palm has now become one of the most important crops, palm oil representing nearly 25% of global plant oil consumption. Many studies have thus addressed oil palm ecophysiology and photosynthesis-based models of carbon allocation have been used. However, there is a lack of experimental data on carbon fixation and redistribution within palm trees, and important C-sinks have not been fully characterized yet. Here, we carried out extensive measurement of natural (13) C-abundance (δ(13) C) in oil palm tissues, including fruits at different maturation stages. We find a (13) C-enrichment in heterotrophic organs compared to mature leaves, with roots being the most (13) C-enriched. The δ(13) C in fruits decreased during maturation, reflecting the accumulation in (13) C-depleted lipids. We further used observed δ(13) C values to compute plausible carbon fluxes using a steady-state model of (13) C-distribution including metabolic isotope effects ((12) v/(13) v). The results suggest that fruits represent a major respiratory loss (≈39% of total tree respiration) and that sink organs such as fruits are fed by sucrose from leaves. That is, glucose appears to be a quantitatively important compound in palm tissues, but computations indicate that it is involved in dynamic starch metabolism rather that C-exchange between organs.
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Affiliation(s)
- Emmanuelle Lamade
- UPR34 Performance of Perennial Cropping Systems, CIRAD-PERSYST, Montpellier, 34398, France
| | - Guillaume Tcherkez
- Research School of Biology, College of Medicine, Biology and Environment, Australian National University, Canberra, Australian Capital Territory, 2601, Australia
| | - Nuzul Hijri Darlan
- Indonesian Oil Palm Research Institute, IOPRI, Jl. Brigjen Katamso 51, Medan, North Sumatra, Indonesia
| | | | - Chantal Fresneau
- ESE, Université Paris-Sud, CNRS UMR 8079, Orsay cedex, 91405, France
| | - Caroline Mauve
- Plateforme Métabolisme-Métabolome, Université Paris-Sud, IPS2, Orsay cedex, 91405, France
| | - Marlène Lamothe-Sibold
- Plateforme Métabolisme-Métabolome, Université Paris-Sud, IPS2, Orsay cedex, 91405, France
| | - Diana Sketriené
- ESE, Université Paris-Sud, CNRS UMR 8079, Orsay cedex, 91405, France
| | - Jaleh Ghashghaie
- ESE, Université Paris-Sud, CNRS UMR 8079, Orsay cedex, 91405, France
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30
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Weise SE, Carr DJ, Bourke AM, Hanson DT, Swarthout D, Sharkey TD. The arc mutants of Arabidopsis with fewer large chloroplasts have a lower mesophyll conductance. PHOTOSYNTHESIS RESEARCH 2015; 124:117-26. [PMID: 25733184 DOI: 10.1007/s11120-015-0110-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Accepted: 02/23/2015] [Indexed: 05/10/2023]
Abstract
Photosynthetic cells of most land plant lineages have numerous small chloroplasts even though most algae, and even the early diverging land plant group the hornworts, tend to have one or a few large chloroplasts. One constraint that small chloroplasts could improve is the resistance to CO2 diffusion from the atmosphere to the chloroplast stroma. We examined the mesophyll conductance (inverse of the diffusion resistance) of mutant Arabidopsis thaliana plants with one or only a few large chloroplasts per cell. The accumulation and replication of chloroplasts (arc) mutants of A. thaliana were studied by model fitting to gas exchange data and (13)CO2 discrimination during carbon fixation. The two methods generally agreed, but the value of the CO2 compensation point of Rubisco (Γ *) used in the model had a large impact on the estimated photosynthetic parameters, including mesophyll conductance. We found that having only a few large chloroplasts per cell resulted in a 25-50 % reduction in the mesophyll conductance at ambient CO2.
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Affiliation(s)
- Sean E Weise
- Department of Biochemistry & Molecular Biology, Michigan State University, 603 Wilson Road, Room 201, East Lansing, MI, 48824, USA
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31
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Raven JA, Griffiths H. Photosynthesis in reproductive structures: costs and benefits. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:1699-705. [PMID: 25871648 PMCID: PMC4669558 DOI: 10.1093/jxb/erv009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Revised: 12/16/2014] [Accepted: 12/19/2014] [Indexed: 05/18/2023]
Abstract
The role of photosynthesis by reproductive structures during grain-filling has important implications for cereal breeding, but the methods for assessing the contribution by reproductive structures to grain-filling are invasive and prone to compensatory changes elsewhere in the plant. A technique analysing the natural abundance of stable carbon isotopes in soluble carbohydrates has significant promise. However, it depends crucially on there being no more than two sources of organic carbon (leaf and ear/awn), with significantly different (13)C:(12)C ratios and no secondary fractionation during grain-filling. The role of additional peduncle carbohydrate reserves represents a potential means for N remobilization, as well as for hydraulic continuity during grain-filling. The natural abundance of the stable isotopes of carbon and oxygen are also useful for exploring the influence of reproduction on whole plant carbon and water relations and have been used to examine the resource costs of reproduction in females and males of dioecious plants. Photosynthesis in reproductive structures is widespread among oxygenic photosynthetic organisms, including many clades of algae and embryophytes of different levels of complexity. The possible evolutionary benefits of photosynthesis in reproductive structures include decreasing the carbon cost of reproduction and 'use' of transpiratory loss of water to deliver phloem-immobile calcium Ca(2+) and silicon [Si(OH)4] via the xylem. The possible costs of photosynthesis in reproductive structures are increasing damage to DNA from photosynthetically active, and hence UV-B, radiation and the production of reactive oxygen species.
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Affiliation(s)
- John A Raven
- Division of Plant Sciences, University of Dundee at the James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK , and School of Plant Biology, University of Western Australia, M048, 35 Stirling Highway, Crawley, WA 6009, Australia
| | - Howard Griffiths
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK
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von Caemmerer S, Evans JR. Temperature responses of mesophyll conductance differ greatly between species. PLANT, CELL & ENVIRONMENT 2015; 38:629-37. [PMID: 25224884 DOI: 10.1111/pce.12449] [Citation(s) in RCA: 163] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 08/19/2014] [Accepted: 08/20/2014] [Indexed: 05/04/2023]
Abstract
The temperature responses of mesophyll conductance (gm ) were investigated for nine species using carbon isotope techniques combining tunable diode laser spectroscopy and gas exchange measurements. Species included the evergreen trees Eucalyptus pauciflora and Quercus engelmannii; the tropical evergreen tree Lophostemon confertus; as well as the herbaceous species Nicotiana tabacum, Oryza sativa, Triticum aestivum, Gossypium hirsutum, Glycine max and Arabidopsis thaliana. Responses varied from a two- to threefold increase in mesophyll conductance between 15 and 40 °C observed for N. tabacum, G. hirsutum, G. max and E. pauciflora to almost no change in L. confertus and T. aestivum. To account for the different temperature responses between species, we suggest that there must be variation in both the activation energy for membrane permeability and the effective pathlength for liquid phase diffusion. Stomatal conductance was relatively independent of increases in leaf temperature and concomitant increases in leaf to air vapour pressure difference. Two exceptions were Eucalyptus and Gossypium, where stomatal conductance increased with temperature up to 35 °C despite increasing leaf to air vapour pressure. For a given species, temperature responses of stomatal and mesophyll conductance were independent of one another.
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Affiliation(s)
- Susanne von Caemmerer
- Division of Plant Sciences, Research School of Biology, The Australian National University, Canberra, Australian Capital Territory, 0200, Australia
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Mizokami Y, Noguchi K, Kojima M, Sakakibara H, Terashima I. Mesophyll conductance decreases in the wild type but not in an ABA-deficient mutant (aba1) of Nicotiana plumbaginifolia under drought conditions. PLANT, CELL & ENVIRONMENT 2015; 38:388-98. [PMID: 24995523 DOI: 10.1111/pce.12394] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Revised: 06/24/2014] [Accepted: 06/25/2014] [Indexed: 05/19/2023]
Abstract
Under drought conditions, leaf photosynthesis is limited by the supply of CO2 . Drought induces production of abscisic acid (ABA), and ABA decreases stomatal conductance (gs ). Previous papers reported that the drought stress also causes the decrease in mesophyll conductance (gm ). However, the relationships between ABA content and gm are unclear. We investigated the responses of gm to the leaf ABA content [(ABA)L ] using an ABA-deficient mutant, aba1, and the wild type (WT) of Nicotiana plumbaginifolia. We also measured leaf water potential (ΨL ) because leaf hydraulics may be related to gm . Under drought conditions, gm decreased with the increase in (ABA)L in WT, whereas both (ABA)L and gm were unchanged by the drought treatment in aba1. Exogenously applied ABA decreased gm in both WT and aba1 in a dose-dependent manner. ΨL in WT was decreased by the drought treatment to -0.7 MPa, whereas ΨL in aba1 was around -0.8 MPa even under the well-watered conditions and unchanged by the drought treatment. From these results, we conclude that the increase in (ABA)L is crucial for the decrease in gm under drought conditions. We discuss possible relationships between the decrease in gm and changes in the leaf hydraulics.
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Affiliation(s)
- Yusuke Mizokami
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, 113-0033, Japan
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34
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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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35
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Barbour MM, Song X. Do tree-ring stable isotope compositions faithfully record tree carbon/water dynamics? TREE PHYSIOLOGY 2014; 34:792-795. [PMID: 25117269 DOI: 10.1093/treephys/tpu064] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Affiliation(s)
- Margaret M Barbour
- Centre for Carbon, Water and Food, The University of Sydney, 380 Werombi Road, Brownlow Hill, NSW 2570, Australia;
| | - Xin Song
- Centre for Carbon, Water and Food, The University of Sydney, 380 Werombi Road, Brownlow Hill, NSW 2570, Australia
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von Caemmerer S, Ghannoum O, Pengelly JJL, Cousins AB. Carbon isotope discrimination as a tool to explore C4 photosynthesis. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:3459-70. [PMID: 24711615 DOI: 10.1093/jxb/eru127] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Photosynthetic carbon isotope discrimination is a non-destructive tool for investigating C4 metabolism. Tuneable diode laser absorption spectroscopy provides new opportunities for making rapid, concurrent measurements of carbon isotope discrimination and CO2 assimilation over a range of environmental conditions, and this has facilitated the use of carbon isotope discrimination as a probe of C4 metabolism. In spite of the significant progress made in recent years, understanding how photosynthetic carbon isotope discrimination measured concurrently with gas exchange relates to carbon isotope composition of leaf and plant dry matter remains a challenge that requires resolution if this technique is to be successfully applied as a screening tool in crop breeding and phylogenetic research. In this review, we update our understanding of the factors and assumptions that underlie variations in photosynthetic carbon isotope discrimination in C4 leaves. Closing the main gaps in our understanding of carbon isotope discrimination during C4 photosynthesis may help advance research aimed at developing higher productivity and efficiency in key C4 food, feed, and biofuel crops.
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Affiliation(s)
- Susanne von Caemmerer
- Research School of Biology, The Australian National University, Canberra ACT 0200, Australia
| | - Oula Ghannoum
- Hawkesbury Institute for the Environment, University of Western Sydney, Hawkesbury campus, Locked Bag 1797, Penrith 2751, NSW, Australia
| | - Jasper J L Pengelly
- Research School of Biology, The Australian National University, Canberra ACT 0200, Australia
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA 99164, USA
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37
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Bellasio C, Griffiths H. Acclimation of C4 metabolism to low light in mature maize leaves could limit energetic losses during progressive shading in a crop canopy. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:3725-36. [PMID: 24591058 PMCID: PMC4085954 DOI: 10.1093/jxb/eru052] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
C4 plants have a biochemical carbon-concentrating mechanism that increases CO2 concentration around Rubisco in the bundle sheath. Under low light, the activity of the carbon-concentrating mechanism generally decreases, associated with an increase in leakiness (ϕ), the ratio of CO2 retrodiffusing from the bundle sheath relative to C4 carboxylation. This increase in ϕ had been theoretically associated with a decrease in biochemical operating efficiency (expressed as ATP cost of gross assimilation, ATP/GA) under low light and, because a proportion of canopy photosynthesis is carried out by shaded leaves, potential productivity losses at field scale. Maize plants were grown under light regimes representing the cycle that leaves undergo in the canopy, whereby younger leaves initially developed under high light and were then re-acclimated to low light (600 to 100 μE·m(-2)·s(-1) photosynthetically active radiation) for 3 weeks. Following re-acclimation, leaves reduced rates of light-respiration and reached a status of lower ϕ, effectively optimizing the limited ATP resources available under low photosynthetically active radiation. Direct estimates of respiration in the light, and ATP production rate, allowed an empirical estimate of ATP production rate relative to gross assimilation to be derived. These values were compared to modelled ATP/GA which was predicted using leakiness as the sole proxy for ATP/GA, and, using a novel comprehensive biochemical model, showing that irrespective of whether leaves are acclimated to very low or high light intensity, the biochemical efficiency of the C4 cycle does not decrease at low photosynthetically active radiation.
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Affiliation(s)
- Chandra Bellasio
- Physiological Ecology Group, Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK
| | - Howard Griffiths
- Physiological Ecology Group, Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK
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38
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Gentsch L, Hammerle A, Sturm P, Ogée J, Wingate L, Siegwolf R, Plüss P, Baur T, Buchmann N, Knohl A. Carbon isotope discrimination during branch photosynthesis of Fagus sylvatica: a Bayesian modelling approach. PLANT, CELL & ENVIRONMENT 2014; 37:1516-1535. [PMID: 24372560 DOI: 10.1111/pce.12262] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Revised: 11/05/2013] [Accepted: 12/04/2013] [Indexed: 06/03/2023]
Abstract
Field measurements of photosynthetic carbon isotope discrimination ((13)Δ) of Fagus sylvatica, conducted with branch bags and laser spectrometry, revealed a high variability of (13)Δ, both on diurnal and day-to-day timescales. We tested the prediction capability of three versions of a commonly used model for (13)Δ [called here comprehensive ((13)(Δcomp)), simplified ((13) Δsimple) and revised ((13)(Δrevised)) versions]. A Bayesian approach was used to calibrate major model parameters. Constrained estimates were found for the fractionation during CO(2) fixation in (13)(Δcomp), but not in (13)(Δsimple), and partially for the mesophyll conductance for CO(2)(gi). No constrained estimates were found for fractionations during mitochondrial and photorespiration, and for a diurnally variable apparent fractionation between current assimilates and mitochondrial respiration, specific to (13)(Δrevised). A quantification of parameter estimation uncertainties and interdependencies further helped explore model structure and behaviour. We found that (13)(Δcomp) usually outperformed (13)(Δsimple) because of the explicit consideration of gi and the photorespiratory fractionation in (13)(Δcomp) that enabled a better description of the large observed diurnal variation (≈9‰) of (13)Δ. Flux-weighted daily means of (13)Δ were also better predicted with (13)(Δcomp) than with (13)(Δsimple).
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Affiliation(s)
- Lydia Gentsch
- Institute of Agricultural Sciences, ETH Zurich, Universitätsstrasse 2, Zurich, 8092, Switzerland; UR1263 Ephyse, INRA, Villenave d'Ornon, 33140, France
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39
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Kromdijk J, Ubierna N, Cousins AB, Griffiths H. Bundle-sheath leakiness in C4 photosynthesis: a careful balancing act between CO2 concentration and assimilation. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:3443-57. [PMID: 24755278 DOI: 10.1093/jxb/eru157] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Crop species with the C4 photosynthetic pathway are generally characterized by high productivity, especially in environmental conditions favouring photorespiration. In comparison with the ancestral C3 pathway, the biochemical and anatomical modifications of the C4 pathway allow spatial separation of primary carbon acquisition in mesophyll cells and subsequent assimilation in bundle-sheath cells. The CO2-concentrating C4 cycle has to operate in close coordination with CO2 reduction via the Calvin-Benson-Bassham (CBB) cycle in order to keep the C4 pathway energetically efficient. The gradient in CO2 concentration between bundle-sheath and mesophyll cells facilitates diffusive leakage of CO2. This rate of bundle-sheath CO2 leakage relative to the rate of phosphoenolpyruvate carboxylation (termed leakiness) has been used to probe the balance between C4 carbon acquisition and subsequent reduction as a result of environmental perturbations. When doing so, the correct choice of equations to derive leakiness from stable carbon isotope discrimination (Δ(13)C) during gas exchange is critical to avoid biased results. Leakiness responses to photon flux density, either short-term (during measurements) or long-term (during growth and development), can have important implications for C4 performance in understorey light conditions. However, recent reports show leakiness to be subject to considerable acclimation. Additionally, the recent discovery of two decarboxylating C4 cycles operating in parallel in Zea mays suggests that flexibility in the transported C4 acid and associated decarboxylase could also aid in maintaining C4/CBB balance in a changing environment. In this paper, we review improvements in methodology to estimate leakiness, synthesize reports on bundle-sheath leakiness, discuss different interpretations, and highlight areas where future research is necessary.
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Affiliation(s)
- Johannes Kromdijk
- Institute for Genomic Biology, University of Illinois, 1206W Gregory drive, Urbana, IL 61801, USA
| | - Nerea Ubierna
- Research School of Biology, The Australian National University, Canberra, ACT, Australia
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA99164-4236, USA
| | - Howard Griffiths
- Physiological Ecology Group, Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB23EA, UK
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Bellasio C, Griffiths H. Acclimation to low light by C4 maize: implications for bundle sheath leakiness. PLANT, CELL & ENVIRONMENT 2014; 37:1046-58. [PMID: 24004447 DOI: 10.1111/pce.12194] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
C4 plants have a biochemical carbon concentrating mechanism (CCM) that increases CO2 concentration around ribulose bisphosphate carboxylase oxygenase (Rubisco) in the bundle sheath (BS). Under limiting light, the activity of the CCM generally decreases, causing an increase in leakiness, (Φ), the ratio of CO2 retrodiffusing from the BS relative to C4 carboxylation processes. Maize plants were grown under high and low light regimes (respectively HL, 600 versus LL, 100 μE m(-2) s(-1) ). Short-term acclimation of Φ was compared from isotopic discrimination (Δ), gas exchange and photochemistry. Direct measurement of respiration in the light, and ATP production rate (JATP ), allowed us use a novel approach to derive Φ, compared with the conventional fitting of measured and predicted Δ. HL grown plants responded to decreasing light intensities with the well-documented increase in Φ. Conversely, LL plants showed a constant Φ, which has not been observed previously. We explain the pattern by two contrasting acclimation strategies: HL plants maintained a high CCM activity at LL, resulting in high CO2 overcycling and increased Φ; LL plants acclimated by down-regulating the CCM, effectively optimizing scarce ATP supply. This surprising plasticity may limit the impact of Φ-dependent carbon losses in leaves becoming shaded within developing canopies.
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Affiliation(s)
- Chandra Bellasio
- Physiological Ecology Group, Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, UK
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41
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Jahan E, Amthor JS, Farquhar GD, Trethowan R, Barbour MM. Variation in mesophyll conductance among Australian wheat genotypes. FUNCTIONAL PLANT BIOLOGY : FPB 2014; 41:568-580. [PMID: 32481014 DOI: 10.1071/fp13254] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2013] [Accepted: 01/14/2014] [Indexed: 06/11/2023]
Abstract
CO2 diffusion from substomatal intercellular cavities to sites of carboxylation in chloroplasts (mesophyll conductance; gm) limits photosynthetic rate and influences leaf intrinsic water-use efficiency (A/gsw). We investigated genotypic variability of gm and effects of gm on A/gsw among eleven wheat (Triticum aestivum L.) genotypes under light-saturated conditions and at either 2 or 21% O2. Significant variation in gm and A/gsw was found between genotypes at both O2 concentrations, but there was no significant effect of O2 concentration on gm. Further, gm was correlated with photosynthetic rate among the 11 genotypes, but was unrelated to stomatal conductance. The effect of leaf age differed between genotypes, with gm being lower in older leaves for one genotype but not another. This study demonstrates a high level of variation in gm between wheat genotypes; 0.5 to 1.0μmolm-2s-1 bar-1. Further, leaf age effects indicate that great care must be taken to choose suitable leaves in studies of genotypic variation in gm and water-use efficiency.
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Affiliation(s)
- Eisrat Jahan
- Faculty of Agriculture and Environment, The University of Sydney, Private Bag 4011, Narellan, NSW 2567, Australia
| | - Jeffrey S Amthor
- Faculty of Agriculture and Environment, The University of Sydney, Private Bag 4011, Narellan, NSW 2567, Australia
| | - Graham D Farquhar
- Research School of Biology, The Australian National University, Biology Place, Canberra, ACT 0200, Australia
| | - Richard Trethowan
- Faculty of Agriculture and Environment, The University of Sydney, Private Bag 4011, Narellan, NSW 2567, Australia
| | - Margaret M Barbour
- Faculty of Agriculture and Environment, The University of Sydney, Private Bag 4011, Narellan, NSW 2567, Australia
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42
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Gu L, Sun Y. Artefactual responses of mesophyll conductance to CO2 and irradiance estimated with the variable J and online isotope discrimination methods. PLANT, CELL & ENVIRONMENT 2014; 37:1231-49. [PMID: 24237289 DOI: 10.1111/pce.12232] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Revised: 10/31/2013] [Accepted: 11/03/2013] [Indexed: 05/04/2023]
Abstract
Studies with the variable J method have reported that mesophyll conductance (gm ) rapidly decreases with increasing intercellular CO2 partial pressures (Ci ) or decreasing irradiance. Similar responses have been suggested with the online isotope discrimination method, although with less consistency. Here we show that even when the true gm is constant, the variable J method can produce an artefactual dependence of gm on Ci or irradiance similar to those reported in previous studies for any of the following factors: day respiration and chloroplastic CO2 photocompensation point are estimated with Laisk method; Ci or electron transport rate is positively biased; net photosynthetic rate is negatively biased; insufficient NADPH is assumed while insufficient ATP limits RuBP regeneration. The isotopic method produces similar artefacts if fractionation of carboxylation or Ci is positively biased or Δ(13) negatively biased. A non-zero chloroplastic resistance to CO2 movement results in a qualitatively different dependence of gm on Ci or irradiance and this dependence is only sensitive at low Ci . We thus cannot rule out the possibility that previously reported dependence of gm on Ci or irradiance is a methodological artefact. Recommendations are made to take advantage of sensitivities of the variable J and isotopic methods for estimating gm .
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Affiliation(s)
- Lianhong Gu
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
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43
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Stutz SS, Edwards GE, Cousins AB. Single-cell C(4) photosynthesis: efficiency and acclimation of Bienertia sinuspersici to growth under low light. THE NEW PHYTOLOGIST 2014; 202:220-232. [PMID: 24384064 DOI: 10.1111/nph.12648] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Accepted: 11/13/2013] [Indexed: 06/03/2023]
Abstract
Traditionally, it was believed that C(4) photosynthesis required two types of chlorenchyma cells to concentrate CO(2) within the leaf. However, several species have been identified that perform C(4) photosynthesis using dimorphic chloroplasts within an individual cell. The goal of this research was to determine how growth under limited light affects leaf structure, biochemistry and efficiency of the single-cell CO(2) -concentrating mechanism in Bienertia sinuspersici. Measurements of rates of CO(2) assimilation and CO(2) isotope exchange in response to light intensity and O(2) were used to determine the efficiency of the CO(2) -concentrating mechanism in plants grown under moderate and low light. In addition, enzyme assays, chlorophyll content and light microscopy of leaves were used to characterize acclimation to light-limited growth conditions. There was acclimation to growth under low light with a decrease in capacity for photosynthesis when exposed to high light. This was associated with a decreased investment in biochemistry for carbon assimilation with only subtle changes in leaf structure and anatomy. The capture and assimilation of CO(2) delivered by the C(4) cycle was lower in low-light-grown plants. Low-light-grown plants were able to acclimate to maintain structural and functional features for the performance of efficient single-cell C(4) photosynthesis.
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Affiliation(s)
- Samantha S Stutz
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
| | - Gerald E Edwards
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
| | - Asaph B Cousins
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
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44
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Gentsch L, Sturm P, Hammerle A, Siegwolf R, Wingate L, Ogée J, Baur T, Plüss P, Barthel M, Buchmann N, Knohl A. Carbon isotope discrimination during branch photosynthesis of Fagus sylvatica: field measurements using laser spectrometry. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:1481-96. [PMID: 24676031 DOI: 10.1093/jxb/eru024] [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] [Indexed: 05/05/2023]
Abstract
On-line measurements of photosynthetic carbon isotope discrimination ((13)Δ) under field conditions are sparse. Hence, experimental verification of the natural variability of instantaneous (13)Δ is scarce, although (13)Δ is, explicitly and implicitly, used from leaf to global scales for inferring photosynthetic characteristics. This work presents the first on-line field measurements of (13)Δ of Fagus sylvatica branches, at hourly resolution, using three open branch bags and a laser spectrometer for CO₂ isotopologue measurements (QCLAS-ISO). Data from two August/September field campaigns, in 2009 and 2010, in a temperate forest in Switzerland are shown. Diurnal variability of (13)Δ was substantial, with mean diurnal amplitudes of ~9‰ and maximum diurnal amplitudes of ~20‰. The highest (13)Δ were generally observed during early morning and late afternoon, and the lowest (13)Δ during midday. An assessment of propagated standard deviations of (13)Δ demonstrated that the observed diurnal variation of (13)Δ was not a measurement artefact. Day-to-day variations of (13)Δ were summarized with flux-weighted daily means of (13)Δ, which ranged from 15‰ to 23‰ in 2009 and from 18‰ to 29‰ in 2010, thus displaying a considerable range of 8-11‰. Generally, (13)Δ showed the expected negative relationship with intrinsic water use efficiency. Diurnal and day-to-day variability of (13)Δ was, however, always better predicted by that of net CO₂ assimilation, especially in 2010 when soil moisture was high and vapour pressure deficit was low. Stomatal control of leaf gas exchange, and consequently (13)Δ, could only be identified under drier conditions in 2009.
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Affiliation(s)
- Lydia Gentsch
- Institute of Agricultural Sciences, ETH Zurich, Universitätsstrasse 2, 8092 Zurich, Switzerland
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45
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Sun W, Ubierna N, Ma JY, Walker BJ, Kramer DM, Cousins AB. The coordination of C4 photosynthesis and the CO2-concentrating mechanism in maize and Miscanthus x giganteus in response to transient changes in light quality. PLANT PHYSIOLOGY 2014; 164:1283-92. [PMID: 24488966 PMCID: PMC3938620 DOI: 10.1104/pp.113.224683] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Accepted: 01/12/2014] [Indexed: 05/07/2023]
Abstract
Unequal absorption of photons between photosystems I and II, and between bundle-sheath and mesophyll cells, are likely to affect the efficiency of the CO2-concentrating mechanism in C4 plants. Under steady-state conditions, it is expected that the biochemical distribution of energy (ATP and NADPH) and photosynthetic metabolite concentrations will adjust to maintain the efficiency of C4 photosynthesis through the coordination of the C3 (Calvin-Benson-Bassham) and C4 (CO2 pump) cycles. However, under transient conditions, changes in light quality will likely alter the coordination of the C3 and C4 cycles, influencing rates of CO2 assimilation and decreasing the efficiency of the CO2-concentrating mechanism. To test these hypotheses, we measured leaf gas exchange, leaf discrimination, chlorophyll fluorescence, electrochromatic shift, photosynthetic metabolite pools, and chloroplast movement in maize (Zea mays) and Miscanthus × giganteus following transitional changes in light quality. In both species, the rate of net CO2 assimilation responded quickly to changes in light treatments, with lower rates of net CO2 assimilation under blue light compared with red, green, and blue light, red light, and green light. Under steady state, the efficiency of CO2-concentrating mechanisms was similar; however, transient changes affected the coordination of C3 and C4 cycles in M. giganteus but to a lesser extent in maize. The species differences in the ability to coordinate the activities of C3 and C4 cycles appear to be related to differences in the response of cyclic electron flux around photosystem I and potentially chloroplast rearrangement in response to changes in light quality.
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Affiliation(s)
- Wei Sun
- Institute of Grassland Science, Northeast Normal University, Key Laboratory of Vegetation Ecology, Ministry of Education, Changchun, Jilin 130024, China (W.S.)
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, Washington 99164 (W.S., N.U., B.J.W., A.B.C.)
- Key Laboratory of Biogeography and Bioresource in Arid Land, Chinese Academy of Sciences, Urumqi 830011, China (J.-Y.M.); and
- Biochemistry and Molecular Biology and Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824 (D.M.K.)
| | | | - Jian-Ying Ma
- Institute of Grassland Science, Northeast Normal University, Key Laboratory of Vegetation Ecology, Ministry of Education, Changchun, Jilin 130024, China (W.S.)
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, Washington 99164 (W.S., N.U., B.J.W., A.B.C.)
- Key Laboratory of Biogeography and Bioresource in Arid Land, Chinese Academy of Sciences, Urumqi 830011, China (J.-Y.M.); and
- Biochemistry and Molecular Biology and Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824 (D.M.K.)
| | - Berkley J. Walker
- Institute of Grassland Science, Northeast Normal University, Key Laboratory of Vegetation Ecology, Ministry of Education, Changchun, Jilin 130024, China (W.S.)
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, Washington 99164 (W.S., N.U., B.J.W., A.B.C.)
- Key Laboratory of Biogeography and Bioresource in Arid Land, Chinese Academy of Sciences, Urumqi 830011, China (J.-Y.M.); and
- Biochemistry and Molecular Biology and Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824 (D.M.K.)
| | - David M. Kramer
- Institute of Grassland Science, Northeast Normal University, Key Laboratory of Vegetation Ecology, Ministry of Education, Changchun, Jilin 130024, China (W.S.)
- School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, Washington 99164 (W.S., N.U., B.J.W., A.B.C.)
- Key Laboratory of Biogeography and Bioresource in Arid Land, Chinese Academy of Sciences, Urumqi 830011, China (J.-Y.M.); and
- Biochemistry and Molecular Biology and Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824 (D.M.K.)
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46
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Ghashghaie J, Badeck FW. Opposite carbon isotope discrimination during dark respiration in leaves versus roots - a review. THE NEW PHYTOLOGIST 2014; 201:751-769. [PMID: 24251924 DOI: 10.1111/nph.12563] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2013] [Accepted: 09/15/2013] [Indexed: 05/13/2023]
Abstract
In general, leaves are (13) C-depleted compared with all other organs (e.g. roots, stem/trunk and fruits). Different hypotheses are formulated in the literature to explain this difference. One of these states that CO2 respired by leaves in the dark is (13) C-enriched compared with leaf organic matter, while it is (13) C-depleted in the case of root respiration. The opposite respiratory fractionation between leaves and roots was invoked as an explanation for the widespread between-organ isotopic differences. After summarizing the basics of photosynthetic and post-photosynthetic discrimination, we mainly review the recent findings on the isotopic composition of CO2 respired by leaves (autotrophic organs) and roots (heterotrophic organs) compared with respective plant material (i.e. apparent respiratory fractionation) as well as its metabolic origin. The potential impact of such fractionation on the isotopic signal of organic matter (OM) is discussed. Some perspectives for future studies are also proposed .
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Affiliation(s)
- Jaleh Ghashghaie
- Laboratoire d'Ecologie, Systématique et Evolution (ESE), CNRS UMR8079, Bâtiment 362, Université de Paris-Sud (XI), F-91405, Orsay Cedex, France
| | - Franz W Badeck
- Consiglio per la Ricerca e la sperimentazione in Agricoltura, Genomics research centre (CRA - GPG), Via San Protaso, 302, 29017, Fiorenzuola d'Arda (PC), Italy
- Potsdam Institute for Climate Impact Research (PIK), PF 60 12 03, 14412, Potsdam, Germany
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47
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Pintó-Marijuan M, Da Silva AB, Flexas J, Dias T, Zarrouk O, Martins-Loução MA, Chaves MM, Cruz C. Photosynthesis of Quercus suber is affected by atmospheric NH3 generated by multifunctional agrosystems. TREE PHYSIOLOGY 2013; 33:1328-1337. [PMID: 24150034 DOI: 10.1093/treephys/tpt077] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Montados are evergreen oak woodlands dominated by Quercus species, which are considered to be key to biodiversity conservation and ecosystem services. This ecosystem is often used for cattle breeding in most regions of the Iberian Peninsula, which causes plants to receive extra nitrogen as ammonia (NH(3)) through the atmosphere. The effect of this atmospheric NH(3) (NH(3atm)) on ecosystems is still under discussion. This study aimed to evaluate the effects of an NH(3atm) concentration gradient downwind of a cattle barn in a Montado area. Leaves from the selected Quercus suber L. trees along the gradient showed a clear influence of the NH(3) on δ(13)C, as a consequence of a strong limitation on the photosynthetic machinery by a reduction of both stomatal and mesophyll conductance. A detailed study of the impact of NH(3atm) on the photosynthetic performance of Q. suber trees is presented, and new mechanisms by which NH(3) affects photosynthesis at the leaf level are suggested.
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Affiliation(s)
- Marta Pintó-Marijuan
- Molecular Ecophysiology Lab. (LEM), Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, 2780-901 Oeiras, Portugal
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48
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Cernusak LA, Ubierna N, Winter K, Holtum JAM, Marshall JD, Farquhar GD. Environmental and physiological determinants of carbon isotope discrimination in terrestrial plants. THE NEW PHYTOLOGIST 2013; 200:950-65. [PMID: 23902460 DOI: 10.1111/nph.12423] [Citation(s) in RCA: 232] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2013] [Accepted: 06/25/2013] [Indexed: 05/05/2023]
Abstract
Stable carbon isotope ratios (δ(13) C) of terrestrial plants are employed across a diverse range of applications in environmental and plant sciences; however, the kind of information that is desired from the δ(13) C signal often differs. At the extremes, it ranges between purely environmental and purely biological. Here, we review environmental drivers of variation in carbon isotope discrimination (Δ) in terrestrial plants, and the biological processes that can either damp or amplify the response. For C3 plants, where Δ is primarily controlled by the ratio of intercellular to ambient CO2 concentrations (ci /ca ), coordination between stomatal conductance and photosynthesis and leaf area adjustment tends to constrain the potential environmentally driven range of Δ. For C4 plants, variation in bundle-sheath leakiness to CO2 can either damp or amplify the effects of ci /ca on Δ. For plants with crassulacean acid metabolism (CAM), Δ varies over a relatively large range as a function of the proportion of daytime to night-time CO2 fixation. This range can be substantially broadened by environmental effects on Δ when carbon uptake takes place primarily during the day. The effective use of Δ across its full range of applications will require a holistic view of the interplay between environmental control and physiological modulation of the environmental signal.
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Affiliation(s)
- Lucas A Cernusak
- Department of Marine and Tropical Biology, James Cook University, Cairns, Qld, Australia
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Evans JR, von Caemmerer S. Temperature response of carbon isotope discrimination and mesophyll conductance in tobacco. PLANT, CELL & ENVIRONMENT 2013; 36:745-56. [PMID: 22882584 DOI: 10.1111/j.1365-3040.2012.02591.x] [Citation(s) in RCA: 152] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The partial pressure of CO2 at the sites of carboxylation within chloroplasts depends on the conductance to CO2 diffusion from intercellular airspace to the sites of carboxylation, termed mesophyll conductance (gm ). We investigated the temperature response of gm in tobacco (Nicotiana tabacum) by combining gas exchange in high light, ambient CO2 in either 2 or 21% O2 with carbon isotope measurements using tuneable diode laser spectroscopy. The gm increased linearly with temperature in 2 or 21% O2 . In 21% O2 , isotope discrimination associated with gm decreased from 5.0 ± 0.2 to 1.8 ± 0.2‰ as temperature increased from 15 to 40 °C, but the photorespiratory contribution to the isotopic signal is significant. While the fractionation factor for photorespiration (f = 16.2 ± 0.7‰) was independent of temperature between 20 and 35 °C, discrimination associated with photorespiration increased from 1.1 ± 0.01 to 2.7 ± 0.02‰ from 15 to 40 °C. Other mitochondrial respiration contributed around 0.2 ± 0.03‰. The drawdown in CO2 partial pressure from ambient air to intercellular airspaces was nearly independent of leaf temperature. By contrast, the increase in gm with increasing leaf temperature resulted in the drawdown in CO2 partial pressure between intercellular airspaces and the sites of carboxylation decreasing substantially at high temperature.
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Affiliation(s)
- John R Evans
- Plant Science Division, Research School of Biology, The Australian National University, Canberra, Australian Capital Territory 0200, Australia.
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Griffiths H, Helliker BR. Mesophyll conductance: internal insights of leaf carbon exchange. PLANT, CELL & ENVIRONMENT 2013; 36:733-735. [PMID: 23387473 DOI: 10.1111/pce.12075] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 01/31/2013] [Indexed: 06/01/2023]
Affiliation(s)
- Howard Griffiths
- Physiological Ecology Group, Department of Plant Sciences, The University of Cambridge, Cambridge CB2 3EA, UK.
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