Melatonin is an important plant growth regulator which plays a key role in plant growth and development. The objective of the current research was to evaluate the effect of foliar application of melatonin (MF) on photosynthetic efficiency, antioxidant defense mechanism, and its relation with leaf senescence in maize crop grown in a semi-arid region. A field experiment was conducted during 2017 and 2018 growth season, where melatonin was applied to the foliage at concentrations of 0 (MF 0 ), 25 (MF 1 ), 50 (MF 2 ), and 75 (MF 3 ) μM at the ninth leaf stage. Foliar application of melatonin significantly improved chlorophyll content, net photosynthetic rate, soluble sugar content, and soluble protein content during the process of leaf senescence. The application of melatonin also enhanced antioxidant enzyme activities including superoxide dismutase, catalase, and peroxidase, while reduced malondialdehyde and reactive oxygen species accumulation. Melatonin foliar application also increased total leaf area per plant, grains per ear, thousand grain weight and grain yield of maize crop in a semi-arid region. The application of melatonin significantly improved photosynthetic activity, antioxidant defense mechanism, and yield of maize crop in a semi-arid region, where the most effective treatment was MF2.

中文翻译：

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半干旱地区叶面喷施褪黑素通过改善抗氧化防御系统和增强光合能力延缓玉米叶片衰老

褪黑激素是一种重要的植物生长调节剂，在植物生长发育中起着关键作用。本研究的目的是评估叶面喷施褪黑激素 (MF) 对半干旱地区玉米作物光合效率、抗氧化防御机制及其与叶片衰老的关系的影响。在 2017 和 2018 生长季节期间进行了田间试验，其中褪黑激素以 0 (MF 0 )、25 (MF 1 )、50 (MF 2 ) 和 75 (MF 3 ) μM 的浓度在第 9叶期。叶面喷施褪黑激素显着​​提高叶片衰老过程中的叶绿素含量、净光合速率、可溶性糖含量和可溶性蛋白质含量。褪黑激素的应用还增强了抗氧化酶的活性，包括超氧化物歧化酶、过氧化氢酶和过氧化物酶，同时减少丙二醛和活性氧的积累。叶面喷施褪黑激素还增加了半干旱地区玉米作物的单株总叶面积、每穗粒数、千粒重和粒产量。褪黑素的施用显着提高了半干旱地区玉米作物的光合活性、抗氧化防御机制和产量，其中最有效的处理是MF2。