Abstract: 【Objective】 In order to study the characteristics of photosynthetic physiology of rice plants under different nitrogen form nutrition and water stress. 【Method】A hydroponic experiment with simulated water stress by PEG(6000) was conducted, the photosynthetic characters and Rubisco content and activity were studied by analyzing carboxylation efficiency (CE), total nitrogen content, soluble protein content and Rubisco content in newly expanded leaf of rice plants. 【Result】 The results showed that, under ammonium nutrition, there was no significant different CE of rice plant between water stress and non-water stress, while Rubisco activity was reduced 13.3% by water stress. However, under nitrate nutrition, both of CE and Rubisco content reduced under water stress, and Rubisco activity reduced 23.0%. Thus, the inhibitory effect on Rubisco activity (CE/Rubisco) of rice plants supplied with ammonium was lower than that of supplied with nitrate. Furthermore, water stress also increased total nitrogen content in newly expanded leaf of rice plants supplied with ammonium, while no effect under nitrate supply. Water stress increased soluble protein content in newly expanded leaf supplied with three nitrogen forms, although no significant effect on the ratio of Rubisco content to soluble protein under ammonium supply, decreased this ratio under nitrate supply. 【Conclusion】Inhibitory effect of water stress on photosynthetic efficiency of rice plants supplied with ammonium was lower than that of supplied with nitrate.

Key words: Nitrogen form, Water stress, Photosynthetic efficiency, Rubisco, Soluble protein