Effects of water stress on photosystem II photochemistry and its thermostability in wheat plants
Effects of water stress on photosystem II photochemistry and its thermostability in wheat plants
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DOI：
10.1093/jexbot/50.336.1199
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发表时间：
1999-07-01
影响因子：
6.9
通讯作者：
Zhang, JH
中科院分区：
文献类型：
--
作者：
Lu, CM;Zhang, JH
采用调节叶绿素荧光、快速荧光诱导动力学和多相荧光瞬态（OJIP）技术评价了小麦植株在水分胁迫和/或热胁迫（25-45℃）下的PSII光化学特性。水分胁迫对PSII光化学的最大量子产率（F-v/F-m）、快速荧光诱导动力学和适应黑暗叶片的多相荧光瞬态没有影响，说明水分胁迫对PSII的初级光化学没有影响。然而，在适应光的叶片中，水分胁迫降低了开放PSII反应中心捕获激发能的效率（F-v'/F-m'）和PSII电子传递的量子产率（phi(PSII)），增加了非光化学猝灭（q(N)），对光化学猝灭（q(P)）没有影响。这表明水分胁迫改变了光适应叶片的PSII光化学，这种改变可能是一种下调光合电子传递以匹配二氧化碳同化减少的机制。此外，水分胁迫也改变了PSII对热胁迫的响应。当温度高于35℃时，水分胁迫叶片的PSII热稳定性显著增强，表现为F-v/F-m、q(P)、F-v′/F-m′和phi（PSII）在水分胁迫叶片中的下降幅度小于水分充足叶片，而上述荧光参数在中度和重度水分胁迫植物间无显著差异。说明中度水分胁迫处理对PSII热稳定性的影响与重度水分胁迫处理相同。结果表明，PSII的热稳定性可能与植物中o -2络合物和反应中心对高温的抗性增强有关。
Modulated chlorophyll fluorescence, rapid fluorescence induction kinetics and the polyphasic fluorescence transients (OJIP) were used to evaluate PSII photochemistry in wheat plants exposed to water stress and/or heat stress (25-45 degrees C). Water stress showed no effects on the maximal quantum yield of PSII photochemistry (F-v/F-m), the rapid fluorescence induction kinetics, and the polyphasic fluorescence transients in dark-adapted leaves, indicating that water stress had no effects on the primary photochemistry of PSII. However, in light-adapted leaves, water stress reduced the efficiency of excitation energy-capture by open PSII reaction centres (F-v'/F-m') and the quantum yield of PSII electron transport (phi(PSII)), increased the non-photochemical quenching (q(N)) and showed no effects on the photochemical quenching (q(P)). This suggests that water stress modified the PSII photochemistry in the light-adapted leaves and such modifications may be a mechanism to down-regulate the photosynthetic electron transport to match a decreased CO2 assimilation. In addition, water stress also modified the responses of PSII to heat stress. When temperature was above 35 degrees C, thermostability of PSII was strongly enhanced in water-stressed leaves, which was reflected in a less decrease in F-v/F-m, q(P), F-v'/F-m' and phi(PSII) in water-stressed leaves than in well-watered leaves, There were no significant variations in the above fluorescence parameters between moderately and severely water-stressed plants, indicating that the moderate water stress treatment caused the same effects on thermostability of PSII as the severe treatment. It was found that increased thermostability of PSII may be associated with an improvement of resistance of the O-2-evolving complex and the reaction centres in water-stressed plants to high temperature.