The plant respiratory chain includes the ATP-coupling cytochrome pathway (CP) and ATP-uncoupling alternative oxidase (AOX). Under high-light (HL) conditions, plants experience photoinhibition, leading to a damaged photosystem II (PSII). The respiratory chain is considered to affect PSII maintenance and photosynthetic electron transport under HL conditions. However, the underlying details remain unclear. In this study, we investigated the respiratory chain functions related to PSII maintenance and photosynthetic electron transport in plants exposed to HL stress. We measured the HL-induced decrease in the maximum quantum yield of PSII in the leaves of wild-type and AOX1a-knockout (aox1a) Arabidopsis thaliana plants in which CP was partially inhibited by a complex-III inhibitor. We also calculated PSII photodamage and repair rate constants. Both rate constants changed when CP was partially inhibited in aox1a plants, suggesting that the respiratory chain is related to both processes. Before HL stress, photosynthetic linear electron flow (LEF) decreased when CP was partially inhibited. After HL stress, aox1a in the presence of the CP inhibitor showed significantly decreased rates of LEF. The electron flow downstream from PSII and on the donor side of photosystem I may have been suppressed. The function of respiratory chain is required to maintain the optimal LEF as well as PSII maintenance especially under the HL stress.

中文翻译：

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线粒体呼吸链在高光胁迫下维持拟南芥叶片中的光合电子流。

植物的呼吸链包括ATP偶联细胞色素途径（CP）和ATP偶联非选择性氧化酶（AOX）。在强光（HL）条件下，植物会受到光抑制，导致光系统II（PSII）受损。呼吸链被认为会影响HL条件下PSII的维持和光合作用电子的运输。但是，基本细节仍不清楚。在这项研究中，我们调查了暴露于HL胁迫的植物中与PSII维持和光合作用电子传递有关的呼吸链功能。我们测量了HL诱导的野生型和AOX1a敲除（aox1a）拟南芥植物叶片中PSII的最大量子产量的下降，其中CP被复合物III抑制剂部分抑制。我们还计算了PSII的光损伤和修复速率常数。当CP被aox1a植物部分抑制时，两个速率常数都会改变，这表明呼吸链与这两个过程有关。在HL胁迫之前，当CP被部分抑制时，光合线性电子流（LEF）降低。HL应激后，在CP抑制剂存在下aox1a的LEF发生率明显降低。PSII下游和光系统I供体侧的电子流可能已被抑制。呼吸链的功能是维持最佳LEF以及PSII维持所必需的，尤其是在HL压力下。在CP抑制剂存在下aox1a的LEF发生率明显降低。PSII下游和光系统I供体侧的电子流可能已被抑制。呼吸链的功能是维持最佳LEF以及PSII维持所必需的，尤其是在HL压力下。在CP抑制剂存在下aox1a的LEF发生率明显降低。PSII下游和光系统I供体侧的电子流可能已被抑制。呼吸链的功能是维持最佳LEF以及PSII维持所必需的，尤其是在HL压力下。