Integrative effects of melatonin and putrescine on vase life and physiological traits in cut alstroemeria ‘Amatista’

This study evaluated the physiological, biochemical traits, molecular responses, and vase life of cut Alstroemeria hybrida 'Amatista' in response to preharvest applications of putrescine and melatonin. A factorial experiment was arranged in a completely randomized design with three replications. The treatments included foliar sprays of putrescine (0, 1.5, and 3 mM), melatonin (0, 50, and 100 µM), and four postharvest sampling times (0, 5, 10, and 15 days). Measured parameters included chlorophyll index, relative fresh weight, solution uptake, ion leakage, malondialdehyde (MDA), hydrogen peroxide (H₂O₂), polyphenol oxidase (PPO) activity, vase life, and the relative expression of chlorophyllase (CHL) and ACC oxidase (ACO) genes. Postharvest senescence was associated with a time-dependent decline in chlorophyll index, water content, and solution uptake, along with increased ion leakage, MDA, H₂O₂ levels, and PPO activity. However, preharvest application of putrescine and melatonin effectively delayed these detrimental changes. Notably, the combined application of 1.5 mM putrescine and 50 µM melatonin resulted in the greatest improvement in postharvest performance, extending vase life from 16.00 to 23.66 days and enhancing physiological and biochemical traits. Moreover, gene expression analysis indicated that these treatments suppressed the expression of CHL and ACO, suggesting a molecular mechanism involved in delayed senescence. Overall, the findings highlight the potential of putrescine and melatonin as eco-friendly preharvest treatments to improve the postharvest quality and longevity of cut Alstroemeria flowers by modulating key physiological, biochemical, and molecular processes.