Plant Gas Exchange Simulator (PGES): A tool for leaf and canopy gas exchange research and education. Contact me for usename and password to download. See the following article for model details.

Kim, S.-H., and J.H. Lieth. 2003. A coupled model of photosynthesis, stomatal conductance, transpiration for a rose leaf (Rosa hybrida L.). Annals of Botany 91 (7): 771-781 (PDF)