Abstract: In order to reveal the relationship between physiological difference and high photosynthetic efficiency in C₃ plant with high expression C₄ pepc, the transgenic rice with high expression of maize C₄ pepc(PC) and the untransformed rice plant Kitaake (WT) were used as the material plants. The upsecond leaves of the rice plants were used to treat by root system during the booting stage. After the treatments of the different concentrations of NO donor, NO synthesis inhibitors and related signal related reagents as well as in the dark for 12 h, the effects of NO on the net photosynthetic rate (P_n), stomatal conductance (G_s) and intercellular CO₂ concentration (C_i) of the test material leaves were measured. The results showed that: P_n of WT and PC increased by 20.8% and 10.7%, respectively under the treatments of 200 μmol·L^-1 SNP(Sodium nitroprusside) and 1 mmol·L^-1 L-Arg (L-Arginine), which was significantly different(p<0.05); However, with increasing the concentrations of SNP and L-Arg, the P_n, G_s and C_i of two rice plants were gradually suppressed. Compared with PC, the P_n of WT was significantly inhibited (p<0.05), but the changes of G_s and C_i were opposite; When treated by 200 μmol·L^-1 SNP and 1 mmol·L^-1 L-Arg as well as SA (salicylic acid) for the test materials, the changes of P_n, G_s and C_i were similar with those under high concentrations of NO donors treatment; Under united 6 mmol·L^-1 EGTA of Ca²⁺ chelator treatment, compared with the PC, the P_n of WT was significantly inhibited at the level (p<0.01), that C_i was opposite (p<0.05). Correlation analysis showed that: The correlationship between the P_n and the G_s in PC was less than that of WT, the determination coefficients were 0.654 9 and 0.773 5; However, The correlationship between the P_n and the C_i in PC was larger than that of WT, the determination coefficients were 0.466 5 and 0.419 6, which implied that there might be different way of the regulation of photosynthesis between PC and WT, especially at lower concentrations of NO in PC, NO might participate in the process of the stomatal movement with high concentration of free Ca²⁺. It can still maintain the stability of P_n in PC under the conditions in stomatal closure.

Key words: rice, high expression of maize C₄ pepc transgenic rice, NO, stomatal movement, net photosynthetic rate