Melatonin enhances vase life and alters physiological responses in peony (Paeonia lactiflora Pall.) cut flowers

Abstract

The postharvest response of two peony cultivars, 'Qi Hua Lu Shuang' and 'Da Fu Gui', to exogenous treatment with three concentrations (25, 50, and 75 μmol·L−1) of melatonin (MT) was evaluated. Both cultivars demonstrated a similar response to MT treatment in terms of delayed senescence, albeit with differing efficacies. The optimal concentration of MT (50 μmol·L−1) extended the vase life of 'Qi Hua Lu Shuang' and 'Da Fu Gui' by 1.6 and 1.2 days, respectively, relative to the control. This treatment also increased maximum flower diameter by 11.76% and 21.26%, respectively, and improved water balance, with 'Qi Hua Lu Shuang' maintaining stability for 6.0 days and 'Da Fu Gui' for 5.7 days longer than the control. Relative electrical conductivity and malondialdehyde (MDA) content, when treated with 50 μmol·L−1 MT, were reduced by 25.25% and 18.03% for 'Qi Hua Lu Shuang', and by 33.96% and 21.47% for 'Da Fu Gui', respectively. At this MT concentration, soluble sugar content peaked at 6.91 mg·g−1 FW for 'Qi Hua Lu Shuang' and 8.12 mg·g−1 FW for 'Da Fu Gui', while soluble protein content reached 5.07 mg·g−1 FW and 7.93 mg·g−1 FW, respectively. Additionally, at the same concentration of MT, the activities of antioxidant enzymes activities (SOD and CAT) were significantly enhanced. SOD activity peaked at 749.61 U·g−1 FW in 'Qi Hua Lu Shuang' and at 652.77 U·g−1 FW in 'Da Fu Gui', while CAT activity showed increases of 31.86% in 'Qi Hua Lu Shuang' and 44.46% in 'Da Fu Gui', compared to the control. These results demonstrate that 50 μmol·L−1 MT optimally delays senescence and preserves the postharvest quality of cut peonies, offering valuable insight for the floral industry.