Drought stress (DS) is the most important abiotic stress affecting yield and quality of tea worldwide. DS causes oxidative stress to cells due to the accumulation of reactive oxygen species (ROS). As non-enzymatic antioxidants, tea catechins can scavenge excess ROS in response to DS. Further, catechin accumulation contributes to the formation of oxidative polymerization products (e.g. theaflavins and thearubigins) that improve the quality of black tea. However, there are no systematic reports on the response of tea catechins to DS. First, we reviewed the available literature on the response of tea plants to DS. Second, we summarized the current knowledge of ROS production in tea leaves under DS and typical antioxidant response mechanisms. Third, we conducted a detailed review of the changes in catechin levels in tea under different drought conditions. We found that the total amounts of catechin and o-quinone increased under DS conditions. We propose that the possible mechanisms underlying tea catechin accumulation under DS conditions include (i) autotrophic formation of o-quinone, (ii) polymerization of proanthocyanidins that directly scavenge excess ROS, and (iii) formation of metal ion complexes and by influencing the antioxidant systems that indirectly eliminate excess ROS. Finally, we discuss ways of potentially improving black tea quality using drought before picking in the summer/fall dry season. In summary, we mainly discuss the antioxidant mechanisms of tea catechins under DS and the possibility of using drought to improve black tea quality. Our review provides a theoretical basis for the production of high-quality black tea under DS conditions. © 2021 Society of Chemical Industry.

中文翻译：

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茶儿茶素对干旱胁迫响应的研究进展

干旱胁迫（DS）是影响全球茶叶产量和质量的最重要的非生物胁迫。由于活性氧 (ROS) 的积累，DS 会对细胞造成氧化应激。作为非酶抗氧化剂，茶儿茶素可以清除多余的 ROS 以响应 DS。此外，儿茶素的积累有助于形成氧化聚合产物（例如茶黄素和茶红素），从而提高红茶的质量。然而，目前还没有关于茶儿茶素对DS反应的系统报道。首先，我们回顾了有关茶树对 DS 反应的现有文献。其次，我们总结了DS下茶叶中ROS产生的当前知识和典型的抗氧化反应机制。第三，我们对不同干旱条件下茶叶中儿茶素含量的变化进行了详细审查。我们发现儿茶素和o -醌在 DS 条件下增加。我们提出在 DS 条件下茶儿茶素积累的可能机制包括（i）o-醌的自养形成，（ii）直接清除过量 ROS 的原花青素的聚合，以及（iii）金属离子络合物的形成和通过影响抗氧化剂间接消除过量 ROS 的系统。最后，我们讨论了在夏季/秋季旱季采摘前利用干旱潜在地提高红茶质量的方法。总之，我们主要讨论DS下茶儿茶素的抗氧化机制以及利用干旱改善红茶品质的可能性。我们的综述为DS条件下生产优质红茶提供了理论依据。© 2021 化学工业协会。