Rate-Limiting Steps of Electron Transport in Chloroplasts during Ontogeny and Senescence of Barley.
Rate-Limiting Steps of Electron Transport in Chloroplasts during Ontogeny and Senescence of Barley.
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大麦个体发育和衰老过程中叶绿体电子传输的限速步骤。
DOI：
10.1104/pp.72.3.795
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发表时间：
1983
期刊：
影响因子：
7.4
通讯作者：
Kenneth J. Scott
中科院分区：
文献类型：
--
作者：
Peter J. Holloway;Donald J. Maclean;Kenneth J. Scott
测定了大麦叶绿素的部分光化学活性和电子载体浓度。类囊体，在个体发育和衰老期间从初生叶分离。从成熟叶片的类囊体产生较高的量子效率比类囊体从过早或衰老的叶子，这种现象似乎并没有引起任何缺乏水裂解酶。在饱和光条件下，从水到光系统I还原侧的非循环电子通量在叶个体发育过程中增加，成熟时达到峰值，衰老时下降。然而，电子通量似乎是有限的，在不同的步骤之前和之后的叶片成熟。在叶片成熟之前，速率限制步骤位于质体对苯二酚再氧化之前。叶片成熟后，非循环电子通量的下降与细胞色素f和B浓度的下降相关（6）。这种相关性，以及对3-（3，4-二氯苯基）-1，1-二甲基脲处理的类囊体中电子进入和退出机制的考虑，表明含有细胞色素f/B（6）的复合物，而不是质体蓝素或P700，是2，6-二氯酚靛酚和二氨基杜烯还原形式的电子进入位点。因此，有人提出，在衰老叶细胞色素f/B（6）含有复合物限制电子传递的限制率的细胞色素f的还原质体氢醌。
Partial photochemical activities and concentrations of electron carriers were measured relative to chlorophyll in barley (Hordeum vulgare L.) thylakoids, isolated from primary leaves during ontogeny and senescence. Thylakoids from mature leaves generated somewhat higher quantum efficiencies than thylakoids from premature or senescing leaves; this phenomenon did not appear to be caused by any deficiency of water-splitting enzyme. Under conditions of saturating light, the noncyclic electron flux from water to the reducing side of photosystem I increased during leaf ontogeny, peaked at maturity, and declined during senescence. However, electron fluxes appeared to be limited at different steps before and after leaf maturity. Before leaf maturity, the rate-limiting step was located prior to the reoxidation of plastohydroquinone. After leaf maturity, the decline in noncyclic electron flux correlated with a decrease in the concentration of cytochromes f and b(6). This correlation, together with a consideration of mechanisms of entry and exit of electrons in 3-(3,4-dichlorophenyl)-1,1-dimethylurea-treated thylakoids, suggests that the cytochrome f/b(6)-containing complex, and not plastocyanin or P700, is the site of entry of electrons from the reduced forms of 2,6-dichlorophenolindophenol and diaminodurene. It is therefore proposed that in senescing leaves the cytochrome f/b(6)-containing complex limited electron transport by constraining the rate of reduction of cytochrome f by plastohydroquinone.