关键词: 芍药(Paeonia lactiflora Pall.), 外源褪黑素, 干旱胁迫, 光合性能, 抗氧化防御, 生理调控

Abstract: To clarify the regulatory effects of exogenous melatonin on the growth and physiology of Paeonia lactiflora seedlings under drought stress, this study employed a two-factor experimental design combining water treatments (normal irrigation and drought stress) with varying melatonin concentrations (0, 50, 100, and 200 μmol/L). ANOVA results indicated that water treatment significantly influenced growth indices, water status, photosynthetic parameters, and oxidative stress-related indicators (P<0.01). Melatonin concentration also exhibited highly significant effects on most parameters (P<0.01). Additionally, a significant interaction between the two factors (P<0.05 or P<0.01) was observed, suggesting that melatonin's regulatory effects strongly depended on water conditions. Drought stress significantly inhibited plant height and leaf area, reduced leaf relative water content and maximum PSII photochemical efficiency, and induced electrolyte leakage and reactive oxygen species accumulation. Exogenous melatonin application significantly alleviated these adverse effects. Among the treatments, the 100 μmol/L concentration demonstrated the optimal comprehensive effect in promoting growth recovery, enhancing net photosynthetic rate and Fv/Fm, reducing malondialdehyde and reactive oxygen species content, and increasing superoxide dismutase and catalase activity. Under normal irrigation conditions, most parameters showed no significant differences among melatonin treatments. In summary, exogenous melatonin significantly regulated Paeonia lactiflora seedlings under drought conditions, with its alleviative effects exhibiting clear concentration and context dependencies.

Key words: Paeonia lactiflora Pall., exogenous melatonin, drought stress, photosynthetic performance, antioxidant defense, physiological regulation