关键词: 低温, 光抑制, 水稻, 剑叶, 叶绿素荧光

Abstract: The possible mechanisms of preventing chilling photoinhibition damage in indica rice varieties with different cold tolerance i.e. Qinghua 6 (cold sensitive) and Guishan’aixuan 3 (cold tolerant)were explored using PAM pulse modulation fluoremeter to analyse its chlorophyll fluorescence in flag leaves. The results indicated that after chilling induced photoinhibition stress the initial fluorescence F_o in the flag leaves was increased and its F_v/F_m ratio was significantly decreased which were greater than those in the dark chilling treatment. Comparing the varieties with different cold tolerance, the rise of F_o and decline of F_v/F_m were more significant in Guishan’aixuan 3 than those of Qinghua 6. However, its F_o and F_v/F_m recovered fast after treating for 5 h at room temperature with weak light (20 μmol photons/m²·s). The fluorescence quenching analysis also expressed that photochemical quenching (q_P) decreased and no photochemical quenching (q_N) increased by chilling photoinhibition. The effect of DTT treatment on q_P was not significant, it markedly inhibited the increase of q_N. The decrease of q_N in Guishan’aixuan 3 was more significant than that of Qinghua 6, but its recovery was faster at room temperature with weak light. It was considered that occurrence of photoinhibition in indica rice was induced by low temperature. It was shown that the degree of chilling photoinhibition was not the only factor to cause cold damage as ability of recovery of the cold tolerance of the varieties also reflected its effect on photoinhibition. Since Guishan’aixuan 3 had a stronger ability of preventing chilling photoinhibition than Qinghua 6, this may be related to the capacity of xanthophyll cycle pool and regulatory role of zeaxantin

Key words: chilling, photoinhibition, rice, flag leaf, chlorophyll fluorescence, heading stage