Abstract:In order to investigate whether the response of photosynthesis of rice leaves to elevated CO2 concentration ([CO2]) is related to nitrogen supply forms, artificial climate growth chambers were used for observing the photosynthesis of newly developed leaves of rice cultivars (japonica rice cultivars:Wuyunjing 23 (WYJ) and Huaidao 5 (HD), indica rice cultivar:Yangdao 6 (YD), and hybrid rice cultivar:Y-Liangyou 6 (Y-LY)) with four treatments (main treatment:ambient[CO2] and elevated[CO2] (+200 μmol/mol), and secondary treatment:nitrate nitrogen and ammonium nitrogen supply). The results showed that elevated[CO2] increased net photosynthetic rate (Pn) of WYJ, HD and Y-LY leaves under nitrate nitrogen treatment and WYJ leaves under ammonium nitrogen treatment, and intercellular[CO2] (Ci) and water use efficiency (WUE) of rice leaves under different Nitrogen supply forms, and the responses of Pn and WUE under nitrate nitrogen treatment were higher than those under ammonium nitrogen treatment. In addition, elevated[CO2] reduced stomatal conductance (gs) and transpiration rate (Tr) of rice leaves, and the responses of gs and Tr of japonica rice cultivars (WYJ and HD) treated with nitrate nitrogen were greater than those of indica rice (YD), and the responses of gs and Tr of hybrid rice cultivar (Y-LY) treated with ammonium nitrogen was greater than those of japonica and indica rice cultivars. The above results indicate that different Nitrogen supply forms can affect the response of photosynthesis of rice leaves to elevated[CO2], and this effect varies widely among rice cultivars.