Experimental study and mathematical simulation of water use efficiency in wheat leaves affected by some environmental factors

By incorporating Ball-Berry model of stomatal conductance into the models of photosynthesis and transpiration, a model of leaf water use efficiency (WUE)as affected by several environmental variables[irradiance(I), vapor pressure deficit(VPD)and atmospheric CO_(2) concentration (Ca)] was constructed. Because the environmental variables influenced the photosynthetic rate and transpiration rate in different ways, the changes of leaf WUE with these factors were quite complicated. The rates of photosynthesis and transpiration of wheat leaves were also measured in the phytotron where the environmental variables were kept within certain ranges, and leaf WUE was calculated therefrom. The results of simulation fitquite well with the measurements except at high Ca.