Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing, 100101, China.
Sci Rep. 2020 Jun 3;10(1):9039. doi: 10.1038/s41598-020-65704-8.
Current understanding of autumn phenological responses to climate change in deciduous tree species remains limited, mainly due to the difficulties in defining autumn events and the lack of knowledge about its mechanism. Here we applied a method based on measuring chlorophyll A (Chla) content in leaf tissue during the entire autumn senescence processes to appropriately quantify autumn phenological processes. Beginning of leaf coloring could be defined as when about 50% of the Chl was lost. End of leaf coloring could be defined as when about 95% of the Chl was lost. Then the mechanism behind the timing of autumn senescence responses to climate change through hormone regulation was studied for the first time. Four dominate deciduous tree species with representative senescence type (Salix babylonica, Ginkgo biloba, Acer mono, Cotinus coggygria) were chosen as the subject of study. Variations in climate factors (temperature, day length, precipitation, humidity) were recorded and nine major endogenous hormones (IAA, IPA, ZR, DHZR, GA, GA, ABA, MeJA, BR) in leaf tissues were monitored during the entire autumn senescence processes. The experimental results verified temperature and day length are the major climate factors affecting autumn phenology. Low temperature and short day length could result in the decrease of ZR level and the increase of ABA level in leaf tissue, which directly trigger/promote senescence. Meanwhile, low temperature and short day length could cause the decrease of MeJA level and the increase of GA and GA level, which regulate the timing of autumn senescence indirectly through ZR, ABA, and IAA. Our study improves the understanding of autumn phenological response to climate change in deciduous trees.
目前对落叶树种秋季物候对气候变化的认识仍然有限，主要是因为难以定义秋季事件，以及对其机制缺乏了解。在这里，我们应用了一种基于测量叶片组织中叶绿素 A (Chla) 含量的方法，以适当量化秋季物候过程。叶片开始变色可以定义为当 Chl 损失约 50%时。叶片完全变色可以定义为当 Chl 损失约 95%时。然后，我们首次通过激素调节研究了气候变化对秋季衰老响应的机制。选择了四种具有代表性衰老类型的主导落叶树种（垂柳、银杏、槭树、黄栌）作为研究对象。记录了气候因素（温度、日照长度、降水、湿度）的变化，并在整个秋季衰老过程中监测了叶片组织中的九种主要内源激素（IAA、IPA、ZR、DHZR、GA、GA、ABA、MeJA、BR）。实验结果验证了温度和日照长度是影响秋季物候的主要气候因素。低温和短日照长度会导致叶片组织中 ZR 水平降低和 ABA 水平升高，直接引发/促进衰老。同时，低温和短日照长度会导致 MeJA 水平降低和 GA 和 GA 水平升高，通过 ZR、ABA 和 IAA 间接调节秋季衰老的时间。我们的研究提高了对落叶树秋季物候对气候变化响应的认识。
