Basil (Ocimum basilicum L.) is a highly important medicinal plant. In this study, the interactional effects of water deficit and melatonin application on growth and physio-biochemical characteristics of basil were investigated. The treatments included three levels of irrigation (100, 75 and 50% of field capacity) and three melatonin concentrations (0, 50 and 100 µmol). Drought stress decreased the dry weight of plants but application of 100 µmol melatonin markedly increased dry weight under these conditions. Melatonin profoundly enhanced plant drought tolerance by stimulating the antioxidant enzymes (catalase, phenylalanine ammonia-lyase, ascorbate peroxidase and polyphenol oxidase) activities and secondary metabolites (total phenol, flavonoid and anthocyanin contents). Furthermore, melatonin application reduced lipid peroxidation and increased the relative water content and photosynthetic pigments, resulting in an improvement of plant dry matter. It is concluded that foliar spraying with melatonin induced the pre-adaptive responses to drought stress followed by regulating antioxidant defense mechanisms.

罗勒（Ocimum basilicum L.）是一种非常重要的药用植物。在本研究中，研究了水分亏缺和褪黑激素施用对罗勒生长和生理生化特性的相互作用影响。处理包括三个灌溉水平（田间持水量的 100%、75% 和 50%）和三个褪黑激素浓度（0、50 和 100 µmol）。干旱胁迫降低了植物的干重，但在这些条件下施用 100 µmol 褪黑激素显着​​增加了干重。褪黑素通过刺激抗氧化酶（过氧化氢酶、苯丙氨酸解氨酶、抗坏血酸过氧化物酶和多酚氧化酶）活性和次生代谢产物（总酚、类黄酮和花青素含量），显着增强植物的耐旱性。此外，褪黑激素的施用减少了脂质过氧化，增加了相对水含量和光合色素，从而改善了植物干物质。结论是，叶面喷洒褪黑激素诱导了对干旱胁迫的预适应反应，随后调节了抗氧化防御机制。