Modelling of Light-driven RuBP Regeneration, Carboxylation and CO2Diffusion for Leaf Photosynthesis

A two-stage model proposed by Thornley on the photosynthetic rate in leaves is modified to include the transport processes of CO2molecules. The model assumes the Rubisco-catalysed consumption of CO2and the light-driven regeneration of 3-PGA producing sugar. The novel feature is the detailed analytical analysis of stationary CO2diffusion in the mesophyll along with respiration. The model is tested against laboratory measurements of CO2exchange rates of single birch leaves and empirical constants entered into the model are assessed by means of the data. To yield a realistic reaction rate constant for carboxylation, the model requires that the diffusion coefficient describing mesophyllic transport must be somewhat larger than CO2diffusivity in pure liquid water.