title: The sensitivity of photosynthesis to O2and CO2concentration identifies strong Rubisco control above the thermal optimum.
abstract: The biochemical model of C3photosynthesis by Farquhar, von Caemmerer and Berry (FvCB) assumes that photosynthetic CO2assimilation is limited by one of three biochemical processes that are not always easily discerned. This leads to improper assessments of biochemical limitations that limit the accuracy of the model predictions. We use the sensitivity of rates of CO2assimilation and photosynthetic electron transport to changes in O2and CO2concentration in the chloroplast to evaluate photosynthetic limitations. Assessing the sensitivities to O2and CO2concentrations reduces the impact of uncertainties in the fixed parameters to a minimum and simultaneously entirely eliminates the need to determine the variable parameters of the model, such as Vcmax, J, or TP. Our analyses demonstrate that Rubisco limits carbon assimilation at high temperatures, while it is limited by triose phosphate utilization at lower temperatures and at higher CO2concentrations. Measurements can be assigned a priori to one of the three functions of the FvCB model, allowing testing for the suitability of the selected fixed parameters of the model. This approach can improve the reliability of photosynthesis models on scales from the leaf level to estimating the global carbon budget.
authors: Plant Science Division, Research School of Biology, The Australian National University, Acton, ACT, 2601, Australia.|Department of Ecology and Evolutionary Biology, The University of Toronto, Toronto, ON, M5S 3B2, Canada.
authors: Florian A
authors: FA
authors: Busch
authors: Department of Ecology and Evolutionary Biology, The University of Toronto, Toronto, ON, M5S 3B2, Canada.
authors: Rowan F
authors: RF
authors: Sage
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D004579:Electron Transport; D027723:Ipomoea batatas / Q000502:physiology*; D008954:Models, Biological; D010100:Oxygen / Q000378:metabolism*; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism*; D013696:Temperature
chemical_list: D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D002245:Carbon Dioxide; D012273:Ribulose-Bisphosphate Carboxylase; D010100:Oxygen
keywords: O2 sensitivity; Rubisco; biochemical model; chlorophyll fluorescence; gas exchange; photosynthesis; triose phosphate utilization