Modeling the Photosynthetic Response of C 3 Leaves to Environmental Factors

Abstract

Photosynthetic properties of individual leave change through time, both as a consequence of leaf aging and in response to a varying environment. This chapter describes a physiologically based model of leaf photosynthesis. The model describes the photosynthetic responses of leaves of C3 plants as affected by incident irradiance, leaf temperature, and the concentrations of CO2 and O2. The model is parameterized for soybean, using a portion of a published data set. The chapter describes estimating values of the remaining parameters from gas-exchange measurements, which have become more or less routine with the development of field-portable photosynthesis systems. Despite a tendency to overestimate photosynthesis when irradiance was low early and late in the day, the overall fit to both CO2 assimilation and leaf conductance was satisfactory. To be useful in predicting leaf gas-exchange responses to varying environmental conditions, the model of CO2 assimilation presented above must be integrated with a model describing stomatal conductance.