黑暗和强光下脱水对小麦离体叶片光系统活性的影响

Effects of Dark and Strong Light Dehydration on the Photosystem Activity in Wheat Leaves in Vitro

脱水是小麦叶片在干旱条件下的自然失水过程,为了探明黑暗和强光下脱水对小麦叶片光系统的影响机制及其差异,采用叶绿素荧光动力学技术,分析了黑暗和强光下脱水不同时间对小麦离体叶片光系统活性的影响。结果表明,强光加速了叶片脱水过程,黑暗脱水条件下,叶片的最大光化学效率随着脱水程度的增加并没有出现明显下降,而强光下显著下降,且随着脱水程度加剧而下降速度逐渐加快;强光脱水条件下,QA到QB电子传递受到抑制,且抑制程度大于黑暗脱水;无论是黑暗还是强光脱水条件,光系统II(PSII)供体侧活性均没有显著变化;PSII单元间的偶联程度在黑暗条件下没有明显变化,在强光脱水条件下则大幅下降。最终表明,脱水导致的PSII活性和光合性能的下降依赖于光照,强光下随着脱水程度的加剧,PSII对光能的吸收和传递活性以及PSII单元间能量偶联程度逐渐下降,而在黑暗条件下,仅严重脱水时才会导致最大光化学效率、反应中心数目以及QA到QB电子传递活性的小幅下降。

Dehydration is the natural process of wheat leaves under drought conditions.In order to explore the mechanism of dark and strong light dehydration on photosynthetic mechanism and their differences in detached wheat leaves,the effects of dehydration with dark and strong light on the activity of wheat photosystem were determined and analyzed by using chlorophyll fluorescence dynamics technology.The results showed that the strong light accelerated the leaf dehydration process.Under the condition of dark dehydration,the maximum photochemical efficiency did not decrease significantly with the increase of dehydration degree,but decreased significantly under strong light,and the decline rate gradually accelerated with the increase of dehydration degree.Under the condition of strong light dehydration,the electron transfer from QA to QB was inhibited,and the degree of inhibition was greater than that of dark dehydration.There was no significant change in photosystem II(PSII)donor side activity under either dark or strong light dehydration conditions.The coupling degree between PSII units did not change significantly under dark conditions,but decreased significantly under strong light dehydration.Finally,it showed that the decline of PSII activity and photosynthetic performance caused by dehydration depended on light,under strong light,with the increase of dehydration degree,the absorption and transfer activity of PSII to light energy and the degree of energy coupling between PSII units gradually decline,while under dark conditions,only severe dehydration will lead to the maximum photochemical efficiency,the number of reaction centers and the electron transfer activity from QA to QB decreased slightly.