College of Grassland Agriculture, Northwest A&F University, Yangling 712100, China.
College of Life Sciences, Northwest A&F University, Yangling 712100, China.
Ecotoxicol Environ Saf. 2022 Sep 1;242:113938. doi: 10.1016/j.ecoenv.2022.113938. Epub 2022 Aug 1.
Salinity is one of the most common factors affecting alfalfa (Medicago sativa L.), and NaCl is one of the main factors of salinity stress which can cause heavy losses in agricultural production in the world. The application of exogenous melatonin (MT) plays a major role in numerous plants against various stress environments. The effects of exogenous MT on the NaCl tolerance of alfalfa treated with the control, 100 µmol L MT, 150 mmol L NaCl, or 150 mmol L NaCl+ 100 µmol L MT were investigated. The results showed that MT increased growth parameters, inhibited chlorophyll degradation and promoted photosynthetic gas exchange parameters (photosynthetic rate, conductance to HO, and transpiration rate) and stomatal opening under NaCl stress. Osmotic regulation substances such as soluble sugar, proline and glycine betaine were the highest in the NaCl treatment and the second in the NaCl+MT treatment. Nitrogen, phosphorus, potassium, calcium and magnesium were reduced and sodium was increased by NaCl, whereas these levels were reversed by the NaCl+MT treatment. MT inhibited cell membrane imperfection, lipid peroxidation and reactive oxygen species (ROS) accumulation caused by NaCl stress. MT up-regulated the gene expression and activity of antioxidant enzymes and increased the content of antioxidant non-enzyme substances to scavenge excessive ROS in NaCl-treated plants. In addition, all indicators interacted with each other to a certain extent and could be grouped according to the relative values. All variables were divided into PC 1 (89.2 %) and PC 2 (4 %). They were clustered into two categories with opposite effects, and most of them were significant variables. Hence, these findings reveal that exogenous MT alleviates the inhibitory effects of NaCl stress on photosynthesis, stomata opening, osmotic adjustment, ion balance and redox homeostasis, enhancing tolerance and growth of alfalfa. Furthermore, it suggests that MT could be implemented to improve the NaCl tolerance of alfalfa.
盐度是影响紫花苜蓿（Medicago sativa L.）的最常见因素之一，而 NaCl 是盐胁迫的主要因素之一，它会在世界范围内对农业生产造成重大损失。外源性褪黑素 (MT) 的应用在许多植物应对各种胁迫环境中起着重要作用。研究了对照、100 μmol L MT、150 mmol L NaCl 或 150 mmol L NaCl+100 μmol L MT 处理的紫花苜蓿对 NaCl 耐受性的影响。结果表明，MT 增加了生长参数，抑制了叶绿素降解，促进了光合气体交换参数（光合速率、HO 导度和蒸腾速率）和气孔开度，提高了光合气体交换参数（光合速率、HO 导度和蒸腾速率）和气孔开度。在 NaCl 胁迫下，渗透调节物质如可溶性糖、脯氨酸和甘氨酸甜菜碱的含量最高，其次是 NaCl+MT 处理。NaCl 降低了氮、磷、钾、钙和镁的含量，增加了钠的含量，而 NaCl+MT 处理则逆转了这些含量。MT 抑制了 NaCl 胁迫引起的细胞膜完整性破坏、脂质过氧化和活性氧（ROS）积累。MT 上调了抗氧化酶的基因表达和活性，增加了抗氧化非酶物质的含量，以清除 NaCl 处理植物中过量的 ROS。此外，所有指标在一定程度上相互作用，可以根据相对值进行分组。所有变量分为 PC 1（89.2%）和 PC 2（4%）。它们分为两个具有相反效果的类别，其中大多数是显著变量。因此，这些发现表明，外源性 MT 减轻了 NaCl 胁迫对光合作用、气孔开度、渗透调节、离子平衡和氧化还原平衡的抑制作用，增强了紫花苜蓿的耐盐性和生长。此外，这表明 MT 可以用于提高紫花苜蓿的耐盐性。
