A cell-based model for the photoacclimation and CO2-acclimation of the photosynthetic apparatus

We have developed a mathematical model based on the underlying mechanisms concerning the responses of the photosynthetic apparatus of a microalga cell which grows under constant incident light intensity and ambient CO2 concentration. Photosynthesis involves light and carbon-fixation reactions which are mutually dependent and affect each other, but existing models for photosynthesis don't account for both reactions at once. Our modeling approach allows us to derive distinct equations for the rates of oxygen production, NADPH production, carbon dioxide fixation, carbohydrate production, and rejected energy, which are generally different. The production rates of the photosynthesis products are hyperbolic functions of light and CO2 concentration. The model predicts that in the absence of photoinhibition, CO2-inhibition, photorespiration, and chlororespiration, a cell acclimated to high light and/or CO2 concentration has higher photosynthetic capacity and lower photosynthetic efficiency than does a cell acclimated to low conditions. This results in crossing between the two curves which represent the oxygen production rates and carbon fixation rates in low and high conditions. Finally, in the absence of photoinhibition and CO2-inhibition, the model predicts the carbohydrate production rate in terms of both light intensity and CO2 concentration. (c) 2005 Elsevier B.V. All rights reserved.