A model for chlorophyll fluorescence and photosynthesis at leaf scale

This paper presents a leaf biochemical model for steady-state chlorophyll fluorescence and photosynthesis of C3 and C4 vegetation. The model is a tool to study the relationship between passively measured steady-state chlorophyll fluorescence and actual photosynthesis, and its evolution during the day. Existing models for chlorophyll fluorescence and photosynthesis are integrated into a relatively simple deterministic model to quantify chlorophyll fluorescence, electron transport, carboxylation and deactivation of antennae in case of light and moisture stress. The model explains the behaviour of the relationship between fluorescence and photosynthesis that has been reported in the literature. Simulations, a sensitivity analysis, and measurements show that variations in total chlorophyll fluorescence correlate well with variations in actual photosynthesis in the late morning and afternoon. Then, photosynthesis is light saturated and limited by stomatal regulation. To calculate the actual photosynthesis rate, an estimate of the maximum carboxylation capacity is needed beside chlorophyll fluorescence.