The net photosynthetic rate (Pn), the apparent quantum yield (AQY), the photochemical efficiency of PSⅡ(Fv/Fm), the quantum yield of PSⅡ electron transport (Ф PSⅡ) and the coefficient of photochemical quenching (qp) were decreased in rice (Oryza sativa L.) leaves under high nocturnal temperature (42±1) ℃ stress, but the relative reduction state of PSⅡ (1-qp) was increased. With the increment of stress time, the chlorophyll content and the binding degree of chlorophyll-protein complex declined gradually, the O2(superoxide radical) production rate and H2O2 content in leaves elevated. The activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) increased for 2-3 days under high temperature stress yet decreased afterwards. The results showed that the photosynthetic efficiency declined in rice leaves under high nocturnal temperature stress with concurrent emergence of the symptom of oxidative damage. The gradual increase of the SOD, POD and CAT activities, as well as that of the ratio of Pr (photo-respiration rate) to Pr+Pn and non-photochemical quenching of chlorophyll fluorescence (NPQ) indicates that those mechanisms related to the changes of these parameters may play an important role in protecting rice leaves from oxidative damage under high nocturnal temperature stress.
夜间高温胁迫对水稻叶片光合机构的影响
郭培国 李荣华
（广州师范学院生物系，广州510405）
夜间高温 (42± 1)℃胁迫后水稻 (Oryzasativa L .)叶片的净光合速率 (Pn)下降 ,表观量子效率 (AQY)、PSⅡ原初光能转化效率 (Fv/Fm)、PSⅡ线性电子传递的量子效率 (ФPSⅡ)、光化学猝灭系数 (qp)下降 ,PSⅡ的相对还原状态 (1-qp)升高。随着夜间高温胁迫时间的延长 ,叶绿素_蛋白复合体的结合度和叶绿素含量逐渐降低 ,叶片中O-·2的生成速率和H2 O2 的含量增加 ;清除活性氧的酶类超氧物歧化酶 (SOD)、过氧化物酶 (POD)和过氧化氢酶 (CAT)在2 - 3d内的夜间高温胁迫下活性升高 ,随着胁迫时间的增加则活性下降。结果表明 :夜间高温胁迫引起水稻叶片光合效率下降 ,出现氧化伤害症状 ;而SOD、POD和CAT活性升高 ,光呼吸速率 (Pr)与Pr+Pn 的比值、叶绿素荧光非光化学猝灭 (NPQ)逐渐增加对水稻叶片是一种保护作用。
关键词： 高温胁迫；水稻；光抑制；活性氧；叶绿素荧光参数；保护
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