Abstract: A chilling-tolerant variety, Xiangnuo 1, and a chilling-susceptible variety, IR50, were used to study the influences of chilling on the photosynthesis rate and chlorophyll fluorescence parameters in rice seedlings. The photosynthetic rate of the seedlings of the two rice varieties decreased dramatically during chilling. Photosynthetic rate decreased by 48.7% and 67.5% in Xiangnuo 1 and IR50, respectively, after they were subject to chilling stress for 2 days. Chlorophyll fluorescence measurements showed that less accumulation of redundant excitation energy in the reaction centers did less harm to the centers and the antenna systems in Xiangnuo 1 under chilling stress. Accordingly, higher qP and qN in Xiangnuo 1 were used to dissipate the redundant excitation energy and protect the reaction centers from chilling injury. However, in chilling-susceptible variety, IR50, qP and qN declined rapidly, while Ex increased as the chilling stress persisted. It indicated that the reaction centers and antenna systems in IR50 were damaged severely under chilling stress, which led to the lower photosynthetic rate.

Key words: chilling, rice, photosynthetic rate, chlorophyll fluorescence

摘要： 选用水稻耐冷品种湘糯1号和冷敏感品种IR50为材料，研究了低温对水稻幼苗光合速率和叶绿素荧光参数的影响。结果表明，低温下水稻两品种的光合速率迅速降低，冷敏感品种比耐冷品种下降幅度更大。低温下湘糯1号PSⅡ反应中心和天线系统受到的伤害轻，反应中心过剩激发能积累少，可藉较高的qP和qN进行过剩光能的耗散，保护光合机构免受低温伤害，而冷敏感品种qP下降快，Ex增加较多，但qN却随低温延长而下降，说明它的反应中心和天线系统都受到了严重的低温伤害，导致光合速率下降。

关键词: 低温, 水稻, 光合速率, 叶绿素荧光