Role of melatonin in mitigating drought stress in <i>Areca catechu</i> L.: insights from integrated physiological, biochemical, and transcriptomic analysis

Melatonin is widely recognized for its role in enhancing plant stress tolerance; however, its potential for mitigating drought stress in <italic>Areca catechu</italic> L. remains underexplored. This study evaluates the application of exogenous melatonin in enhancing drought tolerance in <italic>A. catechu</italic> L. through comprehensive physiological, biochemical, and transcriptomic analyses. Exogenous melatonin application significantly improved relative water content by 52%, total chlorophyll concentration by 19%, and Photosystem II (PSII) activity under drought conditions. Additionally, melatonin enhanced antioxidative defense systems, improving reactive oxygen species (ROS) detoxification. RNA-seq analysis revealed 2,394 up-regulated and 2,245 down-regulated genes under drought stress compared to control conditions. Exogenous melatonin treatment modulated gene expression, with 702 genes up-regulated and 939 down-regulated compared to untreated drought-stressed plants. Enrichment analyses and weighted gene co-expression network analysis (WGCNA) revealed that exogenous melatonin significantly activated critical pathways, including plant hormone signal transduction (ko04075), flavonoid biosynthesis (ko00941), MAPK signaling (ko04016), and starch and sucrose metabolism (ko00500). Collectively, these findings provide a molecular framework for utilizing exogenous melatonin to provide a drought-resistance in <italic>A. catechu</italic>.