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 μmol mol⁻¹ was more than at 350 μmol 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 μmol mol⁻¹ was less than at 350 μmol mol⁻¹. The irradiance-response curves for winter wheat had similar tendency, e.g. at 25 °C and 350 μmol mol⁻¹ both P N and g s almost synchronously reached the maximum values at about 1 600 μmol m⁻² s⁻¹. At 25 °C and 600 μmol mol⁻¹ the I max corresponding to P max and g smax was 2 080 and 1 575 μmol m⁻² s⁻¹, respectively.