Abstract: Photosynthesis, chlorophyll fluorescence characteristics and excitation energy distribution in leaves of rice variety Zhenong 952 were investigated under different cadmium concentration stresses. Under the low Cd concentration (0.1 mmol/L), P_n, F_v/F_m, Φ_PSⅡ and q_N had a slight increase while q_P remained unchanged, indicating that rice under 0.1 mmol/L Cd stress had triggered excitation energy dissipation to protect photosynthetic apparatus from the damage by excess excitation energy. P_n, F_v/F_m and Φ_PSⅡ were significantly decreased as well as q_P and q_N at the high Cd concentration (1.0 mmol/L). In the aspect of excitation energy distribution, both D and Ex increased while P declined significantly. It suggested that under 1.0 mmol/L Cd stress, PSⅡ was injured, and some pathway of excitation energy dissipation was blocked, and excitation energy couldn′t be dissipated efficiently and triggered the overproduction of reactive oxygen species (ROS) which induced the increase of activities of antioxidant enzymes, and led to the aggravation of membrane lipid peroxidation and the chlorophyll structure damage.

Key words: rice, cadmium, photosynthesis, chlorophyll fluorescence characteristics, excitation energy dissipation

摘要： 以浙农952为材料，用水培法研究了不同浓度镉（Cd）胁迫对水稻光合、叶绿素荧光特性和能量分配的影响。结果表明，低浓度Cd（0.1 mmol/L）胁迫下水稻净光合速率（Pn）、Fv/Fm、ΦPSⅡ和qN均略有上升，qP无显著变化，这说明在0.1 mmol/L浓度的Cd胁迫下水稻充分启动了能量耗散途径，耗散了过剩光能，使光合机构免受伤害。高浓度Cd（1.0 mmol/L）处理后Pn 、Fv/Fm、ΦPSⅡ均显著降低，qP和qN也大幅下降，在能量分配方面D和Ex显著上升，P显著下降，这说明在1.0 mmol/L浓度的Cd胁迫下，水稻PSⅡ受到伤害，某些能量耗散途径受阻，过剩的激发能不能及时耗散又导致活性氧的产生，最终引起抗氧化物酶活性的升高和叶绿体结构的破坏。

关键词: 水稻, 镉, 光合作用, 叶绿素荧光特性, 能量耗散