短时低温胁迫对甜椒叶绿体超微结构和光系统的影响

 通过测定荧光参数、膜脂脂肪酸组成、活性氧及相关清除酶活性，研究了短时低温（4 oC）胁迫对冷敏感甜椒叶片光系统的影响。结果表明，6 h低温弱光（100 μmol·m-2·s-1）胁迫结束时光系统II（PSII）最大光化学效率（Fv/Fm）下降35.6%，氧化态的P700下降约60%，而暗中低温处理对二者没有影响。低温弱光胁迫对膜脂脂肪酸组成和叶绿体超微结构的影响均比暗中低温胁迫严重，而活性氧清除酶的活性有所下降，活性氧积累。因此，叶绿体膜系统的完整性与活性氧积累之间可能存在一定的相互关系。低温弱光胁迫引起了PSII和PSI的光抑制，而活性氧的积累可能是氧化态P700下降的一个原因，而且PSI对低温弱光比PSII表现得更敏感。

Effects of Short-Term Chilling Stress on the Photosystems and Chloroplast Ultrastructure in Sweet Pepper

By determining fluorescence parameters, composition of fatty acids, active oxygen species and activities of some antioxidant enzymes, the effects of chilling stress (4 oC) in the low light (100 μmol·m-2·s-1) on chilling-sensitive plants were studied. After 6 h of chilling stress (4 oC) in the low light (100 μmol·m-2·s-1), the maximal photochemical efficiency of PSII (Fv/Fm) of sweet pepper leaves decreased by 35.6%, and the oxidizable P700 decreased by 60%. However, chilling stress in the dark had no effect on both of them. Unsaturation of fatty acids in thylakoid membrane was accelerated, which might be helpful to stabilize photosynthetic apparatus. Distortion and swelling of grana caused by chilling in the dark probably decreased activities of antioxidant enzymes, which resulted in the accumulation of active oxygen species. On the contrary, photooxidation might be related to the disintegration and unstacking of grana. Chilling stress induced photoinhibition of PSII and PSI, and active oxygen species might be one of the factors causing the decrease of the oxidizable P700. PSI seemed to be more sensitive to chilling in the low light than PSII.