REGULATION OF PHOTOSYNTHETIC ELECTRON-TRANSPORT AND PHOTOPHOSPHORYLATION IN INTACT CHLOROPLASTS AND LEAVES OF SPINACIA-OLERACEA L
REGULATION OF PHOTOSYNTHETIC ELECTRON-TRANSPORT AND PHOTOPHOSPHORYLATION IN INTACT CHLOROPLASTS AND LEAVES OF SPINACIA-OLERACEA L
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DOI：
10.1007/bf00389050
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发表时间：
1978-01-01
期刊：
影响因子：
4.3
通讯作者：
KOSTER, S
中科院分区：
文献类型：
--
作者：
HEBER, U;EGNEUS, H;KOSTER, S
在CO2还原过程中，氧通过叶绿体的电子传递链被还原。电子流向氧的速率很低。由于抗霉素A抑制CO2依赖的氧演化，因此在叶绿体中，循环光磷酸化为光合作用提供ATP，而叶绿体不能满足电子流向NADP和氧气还原CO2所需的ATP。抗霉素A对光合作用的抑制作用在强光条件下比弱光条件下更为显著，这表明在强光条件下，循环光磷酸化对光合作用有重要作用。完整叶绿体中的电子循环流动受电子受体的控制。在低光强或远红光照射下，它被接受来自光系统I的电子的底物（如草酰乙酸、亚硝酸盐或氧）所降低。显然，循环电子传递途径对电子疏水性很敏感。在没有电子受体的情况下，远红光照明支持循环电子流，红光抑制循环电子流。光激发光系统II的抑制表明，来自光系统II的电子可以通过循环电子传递途径。氧可以减轻抑制作用，它似乎可以防止循环途径的电子载体过度还原，因此具有重要的调节功能。循环电子传递显然受到精细的氧化还原控制。抑制是由过度氧化和过度还原途径的电子载体引起的。
Oxygen is reduced by the electron transport chain of chloroplasts during CO2 reduction. The rate of electron flow to oxygen is low. Since antimycin A inhibited CO2-dependent oxygen evolution, cyclic photophosphorylation contributes ATP to photosynthesis in chloroplasts which cannot satisfy the ATP requirement of CO2 reduction by electron flow to NADP and to oxygen. Inhibition of photosynthesis by antimycin A was more significant at high than at low light intensities suggesting that cyclic photophosphorylation contributes to photosynthesis particularly at high intensities. Cyclic electron flow in intact chloroplasts is under the control of electron acceptors. At low light intensities or under far-red illumination it is decreased by substrates which accept electrons from photosystem I such as oxaloacetate, nitrite or oxygen. Obviously, the cyclic electron transport pathway is sensitive to electron drainage. In the absence of electron acceptors, cyclic electron flow is supported by far-red illumination and inhibited by red light. The inhibition by light exciting photosystem II demonstrated that the cyclic electron transport pathway is accessible to electrons from photosystem II. Inhibition can be relieved by oxygen which appears to prevent over-reduction of electron carriers of the cyclic pathway and thus has an important regulatory function. Cyclic electron transport is apparently under delicate redox control. Inhibition is caused both by excessive oxidation and by over-reduction of electron carriers of the pathway.