Simulation of leaf photosynthesis of winter wheat on Tibetan Plateau and in North China Plain

Photosynthetic rate of winter wheat was measured in 1995 and 1996 at Lhasa (29°41′N, 91°20′E, 3688 m a.s.l.) on the Tibetan Plateau under the extreme conditions of the highest solar radiation and lowest CO 2 partial pressure on earth. Similar measurements were also made in the North China Plain (Yucheng, 36°57′N, 116°36′E, 28 m a.s.l.) in 1998. It has been shown that photosynthesis was greatly inhibited by high light intensities on the plateau. As diurnal changes in temperature was great, temperature also played an evident role in causing diurnal variation of photosynthesis on the plateau. A mathematical description of declination of maximum photosynthesis with light intensities due to photoinhibition or photooxidation in plant was developed. The relation is integrated into a leaf photosynthesis model, which includes the rate-limiting biochemical processes of photosynthesis and physiological processes of stomatal regulation. Photosynthesis of wheat under field conditions on Tibetan Plateau was simulated. The model was also verified with the observation of photosynthesis of winter wheat leaves in the North China Plain. The result shows that the model can simulate photosynthetic rate of crops in field fairly well. This model provides a method to calculate plant productivity, especially for plants under plateau climate with high solar radiation and it is also applicable to plant grown in places at low altitudes.