Phytochromes are red/far-red reversible photoreceptors essential for plant growth and development. Phytochrome signaling is mediated by the physiologically active far-red-absorbing Pfr form that can be inactivated to the red-absorbing Pr ground state by light-dependent photoconversion or by light-independent thermal reversion, also termed dark reversion. Although the term “dark reversion” is justified by historical reasons and frequently used in the literature, “thermal reversion” more appropriately describes the process of light-independent but temperature-regulated Pfr relaxation that not only occurs in darkness but also in light and is used throughout the review. Thermal reversion is a critical parameter for the light sensitivity of phytochrome-mediated responses and has been studied for decades, often resulting in contradictory findings. Thermal reversion is an intrinsic property of the phytochrome molecules but can be modulated by intra- and intermolecular interactions, as well as biochemical modifications, such as phosphorylation. In this review, we outline the research history of phytochrome thermal reversion, highlighting important predictions that have been made before knowing the molecular basis. We further summarize and discuss recent findings about the molecular mechanisms regulating phytochrome thermal reversion and its functional roles in light and temperature sensing in plants.

植物色素是植物生长和发育必不可少的红色/远红色可逆感光体。植物色素信号传导是由具有生理活性的吸收远红外光的Pfr形式介导的，该形式可通过光依赖的光转化或不依赖光的热转化（也称为暗转化）失活为吸收红色的Pr基态。尽管“暗还原”一词由于历史原因是合理的，并且在文献中经常使用，但“热还原”更恰当地描述了与光无关但受温度调节的Pfr弛豫过程，该过程不仅在黑暗中发生，而且在光照下发生，并且在整个审查中使用。热回复是植物色素介导的反应的光敏性的关键参数，并且已经研究了数十年，常常导致矛盾的发现。热还原是植物色素分子的固有特性，但可以通过分子内和分子间相互作用以及生化修饰（例如磷酸化）进行调节。在这篇综述中，我们概述了植物色素热还原的研究历史，重点介绍了在了解分子基础之前已经做出的重要预测。我们进一步总结和讨论有关调节植物色素热还原的分子机制及其在植物光和温度感测中的功能作用的最新发现。重点介绍了在了解分子基础之前已经做出的重要预测。我们进一步总结和讨论有关调节植物色素热还原的分子机制及其在植物光和温度感测中的功能作用的最新发现。重点介绍了在了解分子基础之前已经做出的重要预测。我们进一步总结和讨论有关调节植物色素热还原的分子机制及其在植物光和温度感测中的功能作用的最新发现。