【摘要】 叶绿体在老化过程中对DCIP的光还原活性逐渐下降,温热加速了活性的丧失,似与光合膜结构在老化过程中的解体和温热加速光合膜的破损有关。从光合链上PSⅡ氧化侧加入人工电子供体DPC,可显著恢复老化叶绿体对DCIP的光还原,如象DPC对被羟胺和Tris处理新鲜叶绿体后的恢复作用一样。似乎老化叶绿体DCIP光还原活性的下降,主要是由于PSⅡ氧化侧那部分光合膜受损所造成。用切断PSⅡ→PS Ⅰ间电子流的抑制剂水杨醛肟处理新鲜和老化叶绿体,对DCIP和Fecy的光还原都有抑制,并以对新鲜叶绿体的抑制更甚,加入DPC不能使新鲜叶绿体的光还原活性恢复,但可使老化叶绿体的光还原活性有显著促进,尤以对DCIP的光还原促进更大。似乎DCIP和Fecy接受电子的部位随叶绿体状态不同而有改变,即新鲜叶绿体主要在PS Ⅰ还原侧,老化叶绿体则主要在PSⅡ还原侧,推测此与光合膜的完整或破损和人工电子受体同膜亲和的难易程度有关。更多还原

【Abstract】 The DCIP-photoreduction activities of chloroplast decreased gradually during the aging process, obviously under the influence of temperature condition. Elevated temperature accelerated the loss of photoreducing activity, hence it is supposed that destruction of membrane structure occurred during the aging process,and an elevated temperature would accelerate membrane destruction.The addition of artificial electron donor DPC to the oxidizing side of PSII of the photosynthetic electron transport chain restored the photoreduction of DCIP by aged chloroplast to a marked degree, in the same way as DPC acted on fresh chloroplasts treated by hydroxylamine and Tris washing which blocked the electron flow from water to PSⅡ reaction center.It seems that the decrease of the photoreducing activity of aged chloroplast is mainly due to the destruction of the part of chloroplast membrance which is closed to the region of electron transport on the oxidizing side of PSⅡ. When fresh and aged chloroplasts were treated with the inhibitor salicylaldoxime to block the electron flow from PSⅡ to PSⅡ, the photoreductions of both DCIP and Fecy were inhibited, the inhibition in fresh chloroplast being stronger. In such a case, the photoreduction in fresh chloroplast was no longer restored by the addition of DPC, but the photoreduction of DCIP and Fecy by aged chloroplast was accelerated, the restoration of photoreduction of DCIP was more pronounced. It seems that the site at which DCIP and Fecy accept electron varies with the change in state of chloroplast. In fresh chloroplast it is mainly on the reducing side of PSⅠ, while in aged chloroplast it is mainly on the reducing side of PSⅡ. It is supposed that the difference may be related to the difference in the integrity of membrane and the accessibility of the electron acceptors to the membrane.更多还原