AOX途径在苹果离体叶片失水过程中的光破坏防御作用

Role of Mitochondrial Alternative Oxidase(AOX)in Photoprotection in Apple Detached Leaf under Water Stress

为探讨线粒体交替氧化酶呼吸途径(AOX途径)对水分胁迫下苹果叶片光破坏的防御作用,以苹果砧木平邑甜茶离体叶片为试材,通过AOX抑制剂水杨基羟肟酸(SHAM)处理,同时测定苹果叶片叶绿素荧光诱导动力学曲线和820nm光的吸收曲线,结合JIP-test分析,探讨了失水过程中AOX途径的光保护作用。结果表明:水分胁迫条件下,平邑甜茶叶片的AOX活性显著增加,SHAM抑制AOX途径后,叶片发生更严重的光抑制;在失水胁迫条件下,平邑甜茶叶片PSⅡ原初光化学反应的量子产额(TRo/ABS)、PSⅡ捕获的电子从Q_A传递到Q_B的概率(ETo/TRo)下降,PSⅡ单位反应中心吸收的光能(ABS/RC)上升,而PSⅠ的最大氧化还原活性(ΔI/I_o)未受影响;SHAM抑制AOX途径后,TRo/ABS和ETo/TRo进一步下降,ABS/RC进一步上升,同时引起了ΔI/I_o的下降。研究认为,水分胁迫条件下,平邑甜茶叶片PSⅡ发生了光抑制,而SHAM处理在加重PSⅡ光抑制的同时,引起了PSⅠ的光抑制;叶片失水过程中,AOX呼吸上调是平邑甜茶叶片的重要光破坏防御机制,特别是对PSⅠ具有重要的保护作用。

The purpose of this study is to explore the role of mitochondrial alternative oxidase（AOX）in photoprotection in apple leaves under water stress.After treated with salicylhydroxamic acid（SHAM）to inhibit the AOX pathway,we studied the effects of AOX pathway on photoprotection in Malushupehensis detached leaves under water stress by simultaneously analyzing chlorophyll a fluorescence transient and light absorbance at 820 nm.The results indicated that water stress induced the up-regulation of AOX activity.The inhibition of AOX pathway caused more severe photoinhibition.Under water stress,maximum quantum yield of primary PSⅡ photochemistry（TRo/ABS）and PSⅡ trapped electron being transferred from Q_Ato Q_B（ETo/TRo）decreased,average absorbed photon flux per PSⅡ reaction center（ABS/RC）increased,while the maximum PSⅠ redox acitity（ΔI/I_o）was not affected.After treated with SHAM toinhibit the AOX pathway,ABS/RC markedly increased,TRo/ABS,ETo/TRo as well asΔI/I_o significantly decreased.It was indicated that under water stress the inhibition of AOX pathway caused more severe photoinhibition,especially to the PSⅠ.Generally,the results demonstrate that the AOX pathway played an important role in the photoprotection in M.hupehensis leaves under water stress,particularly in the photoprotection of PSⅠ.