Melatonin regulates petal senescence in peony (Paeonia lactiflora Pall.) cut flowers via the ROS pathway

This study investigated the role of melatonin (MT) in regulating petal senescence in cut peony ( Paeonia lactiflora ‘Da Fu Gui’) via the reactive oxygen species (ROS) pathway. Flowers treated with 50 μmol L −1 MT were sampled across five vase life stages (S1–S5). MT significantly reduced ROS accumulation, with areas stained by 3,3′-diaminobenzidine and nitroblue tetrazolium at S5 decreasing by 72 % and 46 %, respectively. Hydrogen peroxide and malondialdehyde content decreased by 19 % and 20 %, respectively. Antioxidant enzyme activities increased, including superoxide dismutase (+14 % at S3), catalase (+47 % at S4), and ascorbate peroxidase (+96 % at S5). Glutathione content and the GSH/glutathione disulfide ratio increased significantly, with a 3.5-fold increase at S5. Transcriptome analysis identified 323 and 433 differentially expressed genes at S4 and S5. Gene set enrichment analysis revealed negative enrichment of “reactive oxygen species biosynthetic process” (NES = –1.74, CK4 vs MT4) and “NADPH dehydrogenase (quinone) activity” (NES = –1.67, CK4 vs MT4), suggesting the suppression of ROS production and redox modulation by MT. Quantitative real-time PCR confirmed upregulation of PlSODCC , PlCAT1 , PlAPX1 , PlMDHAR4 , PlGLX1 , PlGSTU9 , and PlAFRR , and downregulation of PlGLOX1 at late stages, specifically at S4 and S5. These results indicate that MT delays petal senescence by enhancing ROS scavenging, maintaining redox homeostasis, and regulating ROS-related gene expression. • Melatonin (MT) reduced ROS accumulation and oxidative damage in peony petals. • MT enhanced antioxidant enzyme activity and AsA–GSH cycle efficiency. • Transcriptome analysis revealed MT-responsive DEGs at stages S4 and S5. • GSEA showed MT regulated ROS biosynthesis and NADPH dehydrogenase activity. • qRT-PCR confirmed MT effects on ROS-related gene expression.