Rapid responses of mesophyll conductance to changes of CO 2 concentration, temperature and irradiance are affected by N supplements in rice

Photosynthesis in C 3 plants is significantly limited by mesophyll conductance ( g m ), which can vary with leaf anatomical traits and nitrogen ( N ) supplements. Several studies have investigated the response of g m to N supplements; however, none examined the implications of N supplements on the response of g m to rapid environmental changes. Here we investigated the effect of N supplement on g m and the response of g m to change of CO 2 , temperature and irradiance in rice. High N supplement ( HN ) increased mesophyll cell wall surface area and chloroplast surface area exposed to intercellular airspace per leaf area, and reduced cell wall thickness. These changes resulted in increased g m . The g m of leaves with HN was more sensitive to changes in CO 2 concentration, temperature and irradiance. The difference in leaf structural features between low N supplement and HN indicates that a rapid change in g m is related to the regulation of diffusion through biological membranes rather than leaf structural features. These results will contribute to an understanding of the determinants of g m response to rapid changes in environmental factors.