Leaf senescence is the ultimate stage in leaf development, accompanied by the degradation and redistribution of nutrients and biological macromolecules. Dopamine (DA), a type of catecholamine, plays a role in responding to various plant stresses through its strong antioxidant capacity. However, the relationship between DA and leaf senescence is poorly understood. Thus, leaves isolated from Malus hupehensis were treated with DA, and a dark-induced senescence experiment was conducted. We first found that 100 μmol L⁻¹ DA was the optimal treatment for delaying leaf senescence. The leaves treated with 100 μmol L⁻¹ DA showed higher chlorophyll content and F_v/F_m, and lower relative electrolyte leakage and malondialdehyde content during dark-induced senescence. DA was able to markedly decrease the expression of senescence associated genes (MdSAG12, MdSAG13, and MdSAG29) and a chlorophyll degradation gene (MdPAO). Compared with untreated leaves, the activity of antioxidant enzymes of leaves under DA treatment was significantly higher, and the level of reactive oxygen species (ROS) was significantly lower. Moreover, DA significantly reduced the content of phytohormones (1-aminocyclopropane-1-carboxylate acid, abscisic acid, salicylic acid, and jasmonic acid) that accelerate senescence during dark treatment and changed the expression of genes involved in phytohormone pathways to inhibit the transmission of signals. In addition, DA treatment significantly reduced the expression of genes related to the degradation of soluble sugar (fructose, glucose, sucrose, and sorbitol), thus significantly increasing the soluble sugar content relative to untreated leaves. Overall, our findings revealed that exogenous dopamine could decrease the expression of SAGs, improve the activity of antioxidant enzymes, reduce ROS levels, and the content of phytohormones that accelerate senescence and their signalling pathways, and decrease the degradation rate of soluble sugar to delay the senescence of apple leaves.

叶片衰老是叶片发育的最终阶段，伴随着营养物质和生物大分子的降解和重新分配。多巴胺 (DA) 是一种儿茶酚胺，通过其强大的抗氧化能力在应对各种植物胁迫方面发挥作用。然而，DA 与叶片衰老之间的关系知之甚少。因此，从湖北海棠中分离出的叶子用 DA 处理，并进行了暗诱导衰老实验。我们首先发现 100 μmol L ⁻¹ DA 是延缓叶片衰老的最佳处理。^{100 μmol L −1} DA处理的叶片表现出更高的叶绿素含量和F _v /F _m，并且在黑暗诱导的衰老过程中相对电解质泄漏和丙二醛含量较低。DA 能够显着降低衰老相关基因（MdSAG12、MdSAG13和MdSAG29）和叶绿素降解基因（MdPAO). 与未处理叶片相比，DA处理叶片抗氧化酶活性显着升高，活性氧（ROS）水平显着降低。此外，DA显着降低了暗处理期间加速衰老的植物激素（1-氨基环丙烷-1-羧酸、脱落酸、水杨酸和茉莉酸）的含量，并改变了参与植物激素途径的基因表达，从而抑制了信号。此外，DA 处理显着降低了与可溶性糖（果糖、葡萄糖、蔗糖和山梨糖醇）降解相关的基因表达，从而显着增加了相对于未处理叶片的可溶性糖含量。总的来说，我们的研究结果表明外源性多巴胺可以降低SAGs，提高抗氧化酶的活性，降低ROS水平，以及加速衰老的植物激素及其信号通路的含量，降低可溶性糖的降解速率，从而延缓苹果叶片的衰老。