水分胁迫下黄瓜叶片光系统_电子传递及其含铁组分变化

黄瓜叶片在水分胁控下随着胁迫程度的加深，细胞膜透性增加。表现出PSⅡ荧光激发光谱特征峰峰值的降低。同时其PSⅡ电子传递速率及PSⅡ氧化则DCIP光还原活性下降。通过对PSⅡ的^57Fe穆斯堡尔谱及其参数进行分析显示；水分胁迫使PSⅡ的^57FeMossbauer谱的Ⅱ，Ⅵ子谱2套双峰消失；铁醌复合物（Fe-Q)、细胞色素b559(Cytb559)由还原态向氧化态转化。以上结果表明：铁醌复合体、Cytb559因光能在PSⅡ色素分子之间共振效率降低及PSⅡ氧化侧的电子受到抑制、不能及时得珐其氧化侧传来的电子，而以高自旋Fe^3 -Q复合物及低自旋氧化型Cytb559的形式存在。致使PSⅡ电子由于含铁复合物的Fe^2 /Fe^3 氧还电热的变化而受到阻抑。

Machanism of Changes on Iron Atom in Photosytem

Upon deeper water stress, cell membrane permeability of cucumber leaves increased, while the lower danictenstic peak of PSⅡ excited fluorescent spectra was found. At the same time,the activity of electron transport and DCIP photoreduction on PSⅡ decreased. The results of 57Fe M　o¨ssbauer spectrum and PSⅡ M　o¨ssbauer Parameter on PSⅡ particles showed that: The two peaks of Ⅱ,Ⅵ spectrum on 57Fe M　o¨ssbauer spectrum disappeared. Iron-quinone complex and Cytb559 are oxidized. The results suggested that since iron-quinone complex and Cytb559 could not obtain electron from PSⅡ donor side in time, which was due to the decreasing efficiency of resonance transport among PSⅡ pigment molecules and the declining velocity of electron transfer on PSⅡ oxidant side , the complex that contains iron atoms was in form of high spin Fe3+-Q and low spin oxidized Cytb559. As a result, electron transfer was inhibited at this site owning to the changes of Fe Ⅲ/FeⅡ midpoint potential.