Abstract:

During the grain-filling period, photosynthesis in rice plants contributes 60%–100% of the final grain carbohydrate, but in the mean time, photo-oxidation caused by low temperature and high light is always suffered by top leaves. So it is same importance to increase the resisting photo-oxidation, as well as to improve net photosynthetic rate (P_n) in this period. In previous works, the progenies (SHPF₆) which had high net photosynthetic rate were obtained from the hybrids Oryza sativa Azucena × Oryza rufipogon Ramper 6. Photosynthetic structures of them have been transformed so that a high G_s can be seen. But it is not known whether these progenies also have a high net photosynthetic rate in the grain-filling period and whether they can resist the photo-oxidation under the high light circumstance after the MV treatment. Thus, in this paper, a MV treatment was applied, photosynthetic parameters and chlorophyll fluorescence were measured to identify the extent of photo-oxidation. The results showed that SHPF₆ had a high P_n under high light in the filling-grain period and the Pn increased with the further increment of light intensity. There was a significant correlation with between and P_n C_i (r = －0.767, P<0.01). After MV treatment, the value of F₀, F_v/F_m and F_v/F₀ changed significantly in Zhonghua 10 (P < 0.05), but not in SHPF₆. All of this results suggested that the method of distant crossing can not only improve the net photosynthetic rate, increase stomatal conductance and promote the efficiency of CO₂ assimilation in the filling-grain period, but also increase the resistance to photo-oxidation.

Key words: Wild cross, Wild rice, Photosynthesis, Photo-oxidation