【摘要】 当小麦黄化幼苗在间歇光（周期为2分钟光、118分钟暗）下转绿二十四小时,获得一种发育不完善的叶绿体膜,将它与发育完善的叶绿体膜相比较,研究了它们的结构、组成与光系统Ⅱ功能的关系。发育不完善的膜,无基粒、而发育完善的膜,具有基粒。后者有较高的叶绿素含量、较低的叶绿素a/b比值,具有叶绿素蛋白复合物T及复合物Ⅱ,而前者完全缺乏复合物Ⅱ。发育不完善的叶绿体膜具有较完善的光系统Ⅰ成份,但明显缺乏高电位的细胞色素b₅₅₉、它们光还原DCPIP的活力比发育完善的膜高二倍多,加DPC人工电子给体,还可提高百分之三十多。以上结果可以得出以下结论:1.发育不完善的膜,缺乏捕获光能的叶绿素a/b蛋白复合物,缺乏基粒;2.在发育不完善的膜中,光系统Ⅰ发育较完善、但水裂解酶系统在整个电子传递链中则处于发育最慢的部分;3.由于发育不完善的膜,缺乏高电位细胞色素b₅₅₉,我们推测它不可能处于电子传递链的主链上,而可能位于光系统Ⅱ的侧链上;4.发育不完善的膜、由于结构简单、自我调控能力弱,不能抵抗恶劣条件,如加抑制剂或在弱光下,光化学活性急剧下降。更多还原

【Abstract】 By exposing etiolated wheat seedlings to intermittent light (cycle of 2 minlight 118 min dark) for 24 hr., we could obtain chloroplasts in their initial stagesof development, These were called incompletely developed chloroplast membranes.They were compared with the completely developed chloroplast membranes.Thylakoid membranes were unstacked in incompletely. developed chloroplasts.Whereas in completely developed chloroplasts a large number of well stacked granamembranes were formed. Chlorophyll content was much higher and the chloro-Phyll a/b ratio was lower in completely developed ones. The incompletely de-veloped chloroplast membranes had no complex Ⅱ (light-harvesting chlorophylla/b protein complex) and high potential Cyt b--559 at all, but they possessed Cyt.b, Cyt. f and low-potential Cyt, b--559. DCPIP-photoreduction activity in incompletely developed chloroplast me-mbranes was as high as the normally developed ones, and was further increasedby 36% after DPC had been added as an artificial electron donor. At the sametime light saturation point of DCPIP-photoreduction in the incompletely developedchloroplast membranes was much higher than that in completely developed ones. From the above results we conclude that: 1: Incompletely developed chloroplast membranes lack light-harvestingcomplex Ⅱ, and stacked membranes. We consider that the formation of light-harvesting complex Ⅱ is a major internal factor in inducing membrane stacking. 2. Photosystem Ⅰ may be developed in incompletely developed chloroplasts,The water-splitting enzyme system is the weakest and slowest developing part ofthe whole electron transport chain. 3. Although Cyt. b--559 HP, which is known to be related to PS-Ⅱ,is totallylacking in the incompletely developed chloroplast membranes, PS-Ⅱ activity hasbeen fully developed so we think it might not be appropriate to locate Cyt. b--559Hp in the main chain of electron transport. It seems to us that the position ofCyt b--559 Hp is restricted within the side chain of electron transport near PS-Ⅱ. 4. A characteristic of incompletely developed membranes is that it is notresistant to severe conditions. For instance, in the presence of chemical inhibitorsor under weak illumination, the photochemical activity would drop down verysignificantly.更多还原