Zhang Pengfei, Liu Lei, Wang Xin, Wang Ziyang, Zhang He, Chen Jingting, Liu Xinyu, Wang Yubo, Li Caifeng
College of Agriculture, Northeast Agricultural University, Harbin 150030, China.
Key Laboratory of Mollisols Agroecology, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China.
Plants (Basel). 2021 Apr 28;10(5):886. doi: 10.3390/plants10050886.
Melatonin has been regarded as a promising substance that enhances the abiotic stress tolerance of plants. However, few studies have devoted attention to the role of melatonin in improving salt tolerance in sugar beets. Here, the effects of different application methods (foliar application (100 μM), root application (100 μM), and combined foliar and root application) of melatonin on the morphological and physiological traits of sugar beets exposed to salt stress were investigated. The results showed that melatonin improved the growth of sugar beet seedlings, root yield and sugar content, synthesis of chlorophyll, photosystem II (PS II) activity, and gas exchange parameters under salt stress conditions. Moreover, melatonin enhanced the capacity of osmotic adjustment by increasing the accumulation of osmolytes (betaine, proline, and soluble sugar). At the same time, melatonin increased the H-pump activities in the roots, thus promoting Na efflux and K influx, which maintained K/Na homeostasis and mitigated Na toxicity. In addition, melatonin strengthened the antioxidant defense system by enhancing the activities of antioxidant enzymes, modulating the ASA-GSH cycle, and mediating the phenylalanine pathway, which removed superoxide anions (O) and hydrogen peroxide (HO) and maintained cell membrane integrity. These positive effects were more pronounced when melatonin was applied by combined foliar and root application. To summarize, this study clarifies the potential roles of melatonin in mitigating salt stress in sugar beets by improving photosynthesis, water status, ion homeostasis, and the antioxidant defense system.
褪黑素被认为是一种有前景的物质，可增强植物对非生物胁迫的耐受性。然而，很少有研究关注褪黑素在提高甜菜耐盐性方面的作用。在此，研究了褪黑素不同施用方法（叶面喷施（100 μM）、根部施用（100 μM）以及叶面和根部联合施用）对盐胁迫下甜菜形态和生理特性的影响。结果表明，褪黑素在盐胁迫条件下改善了甜菜幼苗的生长、根产量和含糖量、叶绿素合成、光系统II（PS II）活性以及气体交换参数。此外，褪黑素通过增加渗透调节物质（甜菜碱、脯氨酸和可溶性糖）的积累增强了渗透调节能力。同时，褪黑素增加了根部的H⁺泵活性，从而促进Na⁺外流和K⁺内流，维持了K⁺/Na⁺稳态并减轻了Na⁺毒性。此外，褪黑素通过增强抗氧化酶活性、调节ASA-GSH循环以及介导苯丙氨酸途径来加强抗氧化防御系统，清除超氧阴离子（O₂⁻）和过氧化氢（H₂O₂）并维持细胞膜完整性。当通过叶面和根部联合施用褪黑素时，这些积极作用更为明显。总之，本研究阐明了褪黑素通过改善光合作用、水分状况、离子稳态和抗氧化防御系统来减轻甜菜盐胁迫的潜在作用。
