缺铁对大豆叶片光合作用和光系统Ⅱ功能的影响(英文)

Effects of Iron Deficiency on Photosynthesis and Photosystem Ⅱ Function in Soybean Leaf

通过气体交换和叶绿素荧光测定研究了缺铁对大豆叶片碳同化和光系统Ⅱ的影响。缺铁条件下大豆光合速率(Pn)大幅下降;最大光化学效率(po)下降幅度较小;荧光诱导动力学曲线发生明显的变化,其中电子传递活性明显下降,K相(VK)相对荧光产量提高。缺铁大豆的天线转化效率(Fv'/Fm')、光化学猝灭系数(qP)和光系统Ⅱ实际光化学效率(ΦPSⅡ)降低,而非光化学猝灭(NPQ)则明显增加。此外,缺铁大豆的光后荧光上升增强。据此,认为铁缺乏伤害了光系统Ⅱ复合物供体侧和受体侧的电子传递;缺铁条件下光系统I环式电子传递的增强可能在维持激发能耗散和ATP供给方面起一定作用。

Gas exchange and chlorophyll a fluorescence in soybean plants were investigated to explore the effects of iron deficiency on photosynthesis and photosystem Ⅱ function in vivo. Iron deficiency induced a drastic decrease in net photosynthesis （Pn）. Compared with norreal plants, the maximal quantum yield of PSII photochemistry （φpo） in iron-deficient plants was only slightly lower; whereas, the efficiency with which a trapped exciton can move an electron into the electron transport chain further than QA^- （ψo） and quantum yield of electron transport beyond QA （φEo） were significantly depressed. Iron deficiency also caused a clear enhancement of the relative variable fluorescence at K step （VK）. When exposed to light, iron-deficient plants had considerably lower efficiency of excitation energy capture by open PSII reaction centers （FV′/Fm′）, quantum yield of PSII electron transport （ФPSII）, and photochemical quenching coefficient （qp）, but markedly higher non-photochemical quenching （NPQ）. In addition, post-illumination transient increase in chlorophyll fluorescence was clearly enhanced in iron-deficient plants. Basing on these data, we suggest that both the donor and the acceptor sides of PSII complex were damaged by iron deficiency; cyclic electron transport around PSI in iron-deficient soybean plants might play an important role in inducing the excitation energy dissipation and meeting the demand for extra ATP as a compensation for the loss of phosphorylation capability.