Leaf senescence is an important process for plants to remobilize a variety of metabolites and nutrients to sink tissues, such as developing leaves, fruits and seeds. It has been suggested that reactive oxygen species (ROS) play an important role in the initiation of leaf senescence. Flag leaves of two different barley varieties, cv. Lomerit and cv. Carina, showed differences in the loss of photosystems and in the production of ROS at a late stage of senescence after significant loss of chlorophyll (Krieger-Liszkay et al. 2015). Here, we investigated photosynthetic electron transport and ROS production in primary leaves of these two varieties at earlier stages of senescence. Comparisons were made between plants grown outside in natural light and temperatures and plants grown in temperature-controlled growth chambers under low light intensity. Alterations in the content of photoactive P700, ferredoxin and plastocyanin (PC) photosynthetic electron transport were analyzed using in vivo near-infrared absorbance changes and chlorophyll fluorescence, while ROS were measured with spin-trapping electron paramagnetic resonance spectroscopy. Differences in ROS production between the two varieties were only observed in outdoor plants, whereas a loss of PC was common in both barley varieties regardless of growth conditions. We conclude that the loss of PC is the earliest detectable photosynthetic parameter of leaf senescence while differences in the production of individual ROS species occur later and depend on environmental factors.

中文翻译：

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在不同生长方式下生长的两个大麦品种，叶片衰老过程中光合电子传递的变化。

叶片衰老是植物重新吸收各种代谢物和养分以沉没组织（例如发育中的叶片，果实和种子）的重要过程。已经表明，活性氧（ROS）在叶片衰老的起始中起着重要作用。两种不同大麦品种的旗叶，简历。Lomerit和简历。叶绿素在叶绿素大量损失后，在衰老的后期显示出光系统损失和活性氧产生的差异（Krieger-Liszkay等。2015）。在这里，我们调查了这两个品种在衰老初期的光合电子传输和活性氧的生产。在自然光和温度下在室外生长的植物与在低光强度下在温度受控的生长室内生长的植物之间进行比较。利用体内近红外吸收率变化和叶绿素荧光分析了光活性P700，铁氧还蛋白和质体蓝素（PC）光合电子传递含量的变化，同时用自旋俘获电子顺磁共振光谱法测量了ROS。仅在室外植物中观察到两个品种之间的ROS产生差异，而在两个大麦品种中，无论其生长条件如何，PC的损失都是常见的。