Integrated morphological, metabolome, and transcriptome analyses revealed the mechanism of exogenous gibberellin promoting petiole elongation in .

(Blume) DC. is a popular vegetable with unique flavor and its leaf is the main product organ. Gibberellin (GA) is an important plant hormone that plays vital roles in regulating the growth of plants. In this study, the plants of water dropwort were treated with different concentrations of GA. The plant height of water dropwort was significantly increased after GA treatment. Anatomical structure analysis indicated that the cell length of water dropwort was elongated under exogenous application of GA. The metabolome analysis showed flavonoids were the most abundant metabolites and the biosynthesis of secondary metabolites were also regulated by GA. The exogenous application of GA altered the gene expressions of plant hormone signal transduction ( and ) and metabolites biosynthesis pathways to regulate the growth of water dropwort. The GA contents were modulated by up-regulating the expression of GA metabolism gene . The differentially expressed genes related to cell wall formation were significantly enriched. A total of 22 cellulose synthase involved in cellulose biosynthesis were identified from the genome of water dropwort. Our results indicated that GA treatment promoted the cell elongation by inducing the expression of cellulose synthase and cell wall formation in water dropwort. These results revealed the molecular mechanism of GA-mediated cell elongation, which will provide valuable reference for using GA to regulate the growth of water dropwort.