Light dependence of carboxylation capacity for C3 photosynthesis models

Authors: Bunce, James

Submitted to: Photosynthetica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2016
Publication Date: 3/14/2016
Citation: Bunce, J.A. 2016. Light dependence of carboxylation capacity for C3 photosynthesis models. Photosynthetica. 54:484-490.

Interpretive Summary: Biochemically-based mathematical models of photosynthesis are widely used in predicting crop and ecosystem responses to climate change. However, the most widely used model of photosynthesis often underestimates the response to rising atmospheric carbon dioxide concentrations. This research shows how the model can be improved by incorporating an improved biochemical understanding of how low light limits photosynthesis. This work will be of interest to scientists predicting plant responses to climate change.

Technical Abstract: Photosynthesis at high light is often modelled by assuming limitation by the maximum capacity of Rubisco carboxylation at low carbon dioxide concentrations, by electron transport capacity at higher concentrations, and sometimes by triose-phosphate utilization rate at the highest concentrations. Photosynthesis at lower light is often modelled simply by assuming that it becomes limited by electron transport. However, it is known that Rubisco can become deactivated at less than saturating light, and it is possible that photosynthesis at low light could be limited by carboxylation capacity rather than by electron transport. This could have important consequences for responses of photosynthesis to carbon dioxide and temperature at low light. In this work photosynthetic responses to carbon dioxide concentration of common bean, quinoa, and soybean leaves measured over a wide range of temperatures and photosynthetic photon flux densities were compared with rates modelled assuming either carboxylation capacity or electron transport limitation at limiting light. In all cases, observed rates of photosynthesis were better predicted by assuming limitation by carboxylation capacity rather than by electron transport at limiting light at the current ambient carbon dioxide concentration and below. This modification of the standard biochemical model was much better at reproducing observed responses of light-limited photosynthesis to carbon dioxide concentrations from pre-industrial to projected future atmospheric concentrations.