Photorespiration, an essential component of plant metabolism, was upregulated under abiotic stress conditions, such as high light or drought. One of the signals for such upregulation was the rise in reactive oxygen species (ROS). Photorespiration was expected to mitigate oxidative stress by reducing ROS levels. However, it was unclear if ROS levels would increase when photorespiration was lowered. Our goal was to examine the redox status in leaves when photorespiratory metabolism was restricted under low O₂ (medium flushed with N₂ gas) or by adding aminooxyacetic acid (AOA), a photorespiratory inhibitor. We examined the impact of low O₂ and AOA in leaves of Arabidopsis thaliana under dark, moderate, or high light. Downregulation of typical photorespiratory enzymes, including catalase (CAT), glycolate oxidase (GO), and phosphoglycolate phosphatase (PGLP) under low O₂ or with AOA confirmed the lowering of photorespiratory metabolism. A marked increase in ROS levels (superoxide and H₂O₂) indicated the induction of oxidative stress. Thus, our results demonstrated for the first time that restricted photorespiratory conditions increased the extent of oxidative stress. We propose that photorespiration is essential to sustain normal ROS levels and optimize metabolism in cellular compartments of Arabidopsis leaves.

光呼吸是植物代谢的重要组成部分，在非生物胁迫条件下（如强光或干旱）上调。这种上调的信号之一是活性氧 （ROS） 的增加。预计光呼吸可以通过降低 ROS 水平来减轻氧化应激。然而，目前尚不清楚当光呼吸降低时 ROS 水平是否会增加。我们的目标是检查在低 O₂ （用 N₂ 气体冲洗的培养基） 或添加光呼吸抑制剂氨基氧乙酸 （AOA） 下限制光呼吸代谢时叶片的氧化还原状态。我们研究了低 O₂ 和 AOA 对拟南芥叶片在暗、中光或高光下的影响。在低 O₂ 或 AOA 下，典型的光呼吸酶下调，包括过氧化氢酶 （CAT） 、乙醇酸氧化酶 （GO） 和磷酸乙醇酸磷酸酶 （PGLP） 证实了光呼吸代谢的降低。ROS 水平 （超氧化物和 H₂O₂） 的显着增加表明氧化应激的诱导。因此，我们的结果首次证明受限的光呼吸条件增加了氧化应激的程度。我们提出光呼吸对于维持正常的 ROS 水平和优化拟南芥叶细胞区室的新陈代谢至关重要。