Department of Plant Biology, Carnegie Institution of Washington, Stanford, California.
Planta. 1968 Jun;79(2):99-112. doi: 10.1007/BF00390153.
Oxygen was taken up by both intact and broken chloroplasts when catalase was posioned. In confirmation of other work we found that oxygen enters the electron transport chain of isolated chloroplasts by oxidizing the primary photoreductant of system I. In isolated intact chloroplasts this reaction proceeds in addition to oxygen evolution by PGA reduction. The reductant produced by photosystem II does not react with oxygen at a significant rate.In normal leaves oxygen depresses chlorophyll fluorescence. However, this depression does not take place in DCMU poisoned leaves or in a mutant having a nonfunctional photosystem II; furthermore, another mutant with a weakly functioning photosystem I gave only a very small fluorescence depression with oxygen. This shows that the site of interaction of oxygen is at the reducing end of the electron transport chain. This view is supported by the extent of the fluorescence depression in leaves as a function of oxygen concentration which is very similar to the oxygen dependence of oxygen uptake by isolated chloroplasts.An oxygen requirement of isolated intact chloroplasts reducing PGA and nitrate was indicated by lower reaction rates and faster decay of activity under nitrogen than under air.
当过氧化氢酶被抑制时，完整和破裂的叶绿体都能吸收氧气。我们发现氧气通过氧化系统 I 的最初光还原剂进入分离的叶绿体的电子传递链，这证实了其他工作。在完整的分离叶绿体中，除了 PGA 还原引起的氧气释放外，该反应还会发生。光系统 II 产生的还原剂不会以显著的速率与氧气反应。在正常叶片中，氧气会抑制叶绿素荧光。然而，在 DCMU 中毒的叶片或无功能光系统 II 的突变体中，不会发生这种抑制；此外，另一个具有较弱光系统 I 的突变体在氧气存在下仅产生非常小的荧光抑制。这表明氧气相互作用的部位在电子传递链的还原端。这一观点得到了叶片中荧光抑制程度随氧气浓度变化的支持，这与分离叶绿体中氧气吸收对氧气的依赖性非常相似。
用氮气处理时，完整的分离叶绿体还原 PGA 和硝酸盐的反应速率降低，活性衰减更快，这表明完整的分离叶绿体需要氧气。
