Leaf stomata play a very important roll in plant physiological activities and the interaction between plant and atmosphere. In one hand, plants get CO2 for photosynthesis through stomata. In the other hand, stomata control the water losses causing by transpiration. So that, stomata is not only the key element controlling transpiration and latent heat flux, but also the key factor for photosynthesis. Evidences indicate that besides plant physiological traits, stomatal conductance is very sensitive to environmental elements such as photosynthesis active radiation (PAR), relative humility (RH), air temperature (Ta), leaf temperature (Tl), ambient CO2 concentration etc.