氧气在黑暗-水淹诱导植物叶片光合机构损伤中的作用

本研究排除了光照和根部信号的影响，在完全黑暗条件下对离体叶片进行水淹处理，并在处理过程中分别通入空气或者氮气来控制水淹过程中水中的含氧量。通过分析叶片叶绿素含量、活性氧含量以及叶片光化学活性的变化，探讨叶片水淹时水中缺氧因素对叶片光合机构的直接影响及作用机制。结果表明，与放置在湿润空气中的对照叶片相比，黑暗-水淹处理叶片的最大光化学效率（Fv/Fm）、捕获的激子将电子传递到QA以后的其他电子受体的概率（ψo）均发生显著下降。然而，黑暗．水淹处理36h后，叶片的叶绿素含量并未下降，叶片中H2O2含量也未大量增加。另外，黑暗一水淹导致的叶片光化学活性的下降随着水中含氧量下降的加剧而加剧，补充氧气可以缓解甚至消除这一伤害。这表明黑暗．水淹处理过程中叶片光合机构的伤害与叶片衰老或活性氧的积累无关，而是由于水中缺氧因素对光合机构的直接伤害所致。

Effect of Oxygen on the Damage of Photosynthetic Apparatus in Plant Leaves Induced by Dark-Submergence

Having excluded influence of light and root signals, in this study, we submerged the detached leaves in the dark-submergence treatment （DST）, and pumped air or N2 to control the oxygen content in the water, re- spectively. By analyzing changes of chlorophyll content, ROS content, and photochemical activities of the dark- submerged leaves, we explored the direct effect and mechanism of the hypoxia condition on photosynthetic ap- paratus of leaves during leaf submergence stress. The results showed that both the maximum quantum yield of PSII （Fv/Fm） and efficiency of electron moves beyond QA- （ψo） decreased significantly in leaves after DST com- pared with the control leaves. However, the chlorophyll content remained unchanged and the H2O2 concentra- tion did not increase in the leaves. In addition, the decline of photochemical activities of leaves after DST was aggravated with the decrease of oxygen content in the water, and it could be alleviated or eliminated by oxygen supply. These results indicate that the damage of photosynthetic apparatus in leaves induced by dark-submer- gence was not related to leaf senescence and over-accumulation of ROS, but caused by the direct effect of hy- poxia in the water.