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

摘要： 以具不同抗冷力的籼稻品种青华6号(冷敏感)和桂山矮选3(抗冷)为材料，采用PAM调制荧光仪检测叶片叶绿素荧光的分析方法，探讨不同抗冷力的籼稻品种防御低温光抑制的可能机制。结果表明，籼稻抽穗期剑叶经低温光抑制胁迫后，与黑暗低温处理比较，光照低温处理引起的初始荧光Fo上升，Fv/Fm比值下降明显。抗冷的桂山矮选3比冷敏感的青华6号的Fo上升和Fv/Fm下降的幅度较为显著，但在常温弱光下其恢复较快。荧光猝灭分析亦表明，低温光抑制胁迫引起光化学猝灭qP下降，非光化学猝灭qN受抑制明显，但恢复较快一些。由此可认为，低温诱导籼稻光抑制发生，低温光抑制的程度不完全是伤害的结果，其恢复能力的强弱更能准确地反映品种间抗光抑制的能力。桂山矮选3比青华6号具有较强的防御低温光抑制的能力可能与叶黄素循环库的大小以及玉米黄质的调节作用有关。

关键词: 低温, 光抑制, 水稻, 剑叶, 叶绿素荧光