A coupled model of stomatal conductance and photosynthesis for winter wheat

The model couples stomatal conductance (g(s)) and net photosynthetic rate (P-N) describing not only part of the curve up to and including saturation irradiance (I-max), but also the range above the saturation irradiance. Maximum stomatal conductance (g(smax)) and I-max can be calculated by the coupled model. For winter wheat ( Triticum aestivum) the fitted results showed that maximum P-N (P-max) at 600 mu mol mol(-1) was more than at 350 mu mol mol(-1) under the same leaf temperature, which can not be explained by the stomatal closure at high CO2 concentration because g(smax) at 600 mu mol mol(-1) was less than at 350 mu mol mol(-1). The irradiance-response curves for winter wheat had similar tendency, e. g. at 25 degrees C and 350 mu mol mol(-1) both P-N and g(s) almost synchronously reached the maximum values at about 1 600 mu mol m(-2) s(-1). At 25 degrees C and 600 mu mol mol(-1) the I-max corresponding to P-max and g(smax) was 2 080 and 1 575 mu mol m(-2) s(-1), respectively.