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A model of photosynthetic CO₂ assimilation in C₃ leaves accounting for respiration and energy recycling by the plastidial oxidative pentose phosphate pathway 2023 (English)In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 239, no 2, p. 518-532Article in journal (Refereed) Published

Abstract [en]

• Recently, we reported estimates of anaplerotic carbon flux through the oxidative pentose phosphate pathway (OPPP) in chloroplasts into the Calvin–Benson cycle. These estimates were based on intramolecular hydrogen isotope analysis of sunflower leaf starch. However, the isotope method is believed to underestimate the actual flux at low atmospheric CO₂ concentration (C_a).
• Since the OPPP releases CO₂ and reduces NADP⁺, it can be expected to affect leaf gas exchange under both rubisco- and RuBP-regeneration-limited conditions. Therefore, we expanded Farquhar-von Caemmerer–Berry models to account for OPPP metabolism. Based on model parameterisation with values from the literature, we estimated OPPP-related effects on leaf carbon and energy metabolism in the sunflowers analysed previously.
• We found that flux through the plastidial OPPP increases both above and below C_a ≈ 450 ppm (the condition the plants were acclimated to). This is qualitatively consistent with our previous isotope-based estimates, yet gas-exchange-based estimates are larger at low C_a.
• We discuss our results in relation to regulatory properties of the plastidial and cytosolic OPPP, the proposed variability of CO₂ mesophyll conductance, and the contribution of day respiration to the A/C_i curve drop at high C_a. Furthermore, we critically examine the models and parameterisation and derive recommendations for follow-up studies.

Place, publisher, year, edition, pages

John Wiley & Sons, 2023. Vol. 239, no 2, p. 518-532

Keywords [en]

NADPH ratio, Calvin– Benson cycle, CO2 mesophyll conductance, day respiration, Farquhar-von Caemmerer– Berry photosynthesis model, glucose-6- phosphate shunt, net CO2 assimilation, oxidative pentose phosphate pathway

National Category

Botany Biochemistry Molecular Biology

Identifiers

URN: urn:nbn:se:umu:diva-208439DOI: 10.1111/nph.18965ISI: 000993807900001PubMedID: 37219361Scopus ID: 2-s2.0-85159912517OAI: oai:DiVA.org:umu-208439DiVA, id: diva2:1758989

Available from: 2023-05-24 Created: 2023-05-24 Last updated: 2025-02-20Bibliographically approved

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Wieloch, ThomasSchleucher, Jürgen

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Wieloch, ThomasAugusti, AngelaSchleucher, Jürgen

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Umeå Plant Science Centre (UPSC)Department of Medical Biochemistry and Biophysics

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New Phytologist

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BotanyBiochemistryMolecular Biology

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