COUPLING BIOCHEMICAL AND BIOPHYSICAL PROCESSES AT THE LEAF LEVEL - ANEQUILIBRIUM PHOTOSYNTHESIS MODEL FOR LEAVES OF C-3 PLANTS

The paper presents a generic computer model for estimating short-term steady-state fluxes of CO2, water vapor, and heat from broad leaves an d needle-leaved coniferous shoots of C-3 plant species. The model expl icitly couples all major processes and feedbacks known to impact leaf biochemistry and biophysics including biochemical reactions, stomatal function, and leaf-boundary layer heat- and mass-transport mechanisms. The ability of the model to successfully predict measured photosynthe sis and stomatal-conductance data as well as to simulate a variety of observed leaf responses is demonstrated. A model application investiga ting physiological and environmental regulation of leaf water-use effi ciency (WUE) under steady-state conditions is discussed. Simulation re sults suggest that leaf physiology has a significant control over the environmental sensitivity of leaf WUE. The implementation of a highly efficient solution technique allows the model to be directly incorpora ted into plant-canopy and terrestrial ecosystem models.