A MODEL 2DLEAF OF LEAF GAS-EXCHANGE - DEVELOPMENT, VALIDATION, AND ECOLOGICAL APPLICATION

A two-dimensional model (2DLEAF) of leaf photosynthesis and transpirat ion has been developed that explicitly accounts for gas diffusion thro ugh the boundary layer and the intercellular space as well as for stom atal regulation. The model has been validated for tomato. It was used to study the effect of stomatal density on photosynthesis and transpir ation rate. It has been demonstrated by varying stomatal density in th e model that the stomatal density measured on tomato leaves provides t he maximal photosynthesis rate for both 300 and 600 mu l l(-1) [CO2]. The transpiration rate varied in direct proportion to stomatal density at all values of stomatal aperture, but transpiration efficiency (pho tosynthesis rate/transpiration rate) was higher at 600 mu l l(-1) [CO2 ] with a normal stomatal density than at 300 mu l l(-1) [CO2] with a s tomatal density reduced 25%, Such calculations with 2DLEAF can be usef ul for analysis of contradicting data presented in publications on pos sible changes in stomatal density in a future high [CO2] atmosphere.