水分胁迫下黄瓜叶片光系统Ⅱ电子传递及其含铁组分变化

Machanism of Changes on Iron Atom in PhotosytemⅡ Particles of Cucumber Leaves Under Water Stress

黄瓜叶片在水分胁迫下随着胁迫程度的加深 ,细胞膜透性增加。表现出 PS 荧光激发光谱特征峰峰值的降低。同时其 PS 电子传递速率及 PS 氧化侧 DCIP光还原活性下降。通过对 PS 的 57Fe穆斯堡尔谱及其参数进行分析显示 :水分胁迫使 PS 的 57Fe Mo¨ ssbauer谱的 , 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 PS 色素分子之间共振传递效率降低及 PS 氧化侧的电子传递受到抑制 ,不能及时得到从其氧化侧传来的电子 ,而以高自旋 Fe3 +- Q复合物及低自旋氧化型 Cytb559的形式存在。致使 PS 电子传递由于含铁复合物的 Fe2 +/Fe3

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 57 Fe M o ¨ssbauer spectrum and PSⅡ M o ¨ssbauer Parameter on PSⅡ particles showed that: The two peaks of Ⅱ,Ⅵ spectrum on 57 Fe M o ¨ssbauer spectrum disappeared. Iron quinone complex and Cytb 559 are oxidized. The results suggested that since iron quinone complex and Cytb 559 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 Fe 3+ Q and low spin oxidized Cytb 559 . As a result, electron transfer was inhibited at this site owning to the changes of Fe Ⅲ/FeⅡ midpoint potential.