Leaf Photosynthesis and Its Temperature Response Are Different between Growth Stages and N Supplies in Rice Plants

Leaf photosynthesis is highly correlated with CO(2)-diffusion capacities, which are determined by both leaf anatomical traits and environmental stimuli. In the present study, leaf photosynthetic rate (A), stomatal conductance (g(s)), mesophyll conductance (g(m)) and the related leaf anatomical traits were studied on rice plants at two growth stages and with two different N supplies, and the response of photosynthesis to temperature (T) was also studied. We found that g(m) was significantly higher at mid-tillering stage and at high N treatment. The larger g(m) was related to a larger chloroplast surface area facing intercellular air spaces and a thinner cell wall in comparison with booting stage and zero N treatment. At mid-tillering stage and at high N treatment, g(m) showed a stronger temperature response. The modelling of the g(m)-T relationships suggested that, in comparison with booting stage and zero N treatment, the stronger temperature response of g(m) was related to the higher activation energy of the membrane at mid-tillering stage and at high N treatment. The findings in the present study can enhance our knowledge on the physiological and environmental determinants of photosynthesis.