Melatonin-mediated improvement of ionic homeostasis and antioxidant defense ‎enhances salinity tolerance in Damask Rose (Rosa damascene)‎

This study investigated the role of melatonin in alleviating salinity stress in Rosa damascena. A factorial experiment was conducted in a completely randomized design with three replications, combining four salinity levels (۰, ۶۰, ۱۲۰, and ۱۸۰ mM NaCl) and three melatonin concentrations (۰, ۱۵۰, and ۲۵۰ μM). Salinity significantly inhibited shoot and root growth, reduced chlorophyll and carotenoid contents, and decreased relative water content (RWC), while increasing electrolyte leakage, proline, malondialdehyde (MDA), and sodium accumulation. Melatonin application significantly alleviated these adverse effects. Under non-saline conditions, ۲۵۰ μM melatonin enhanced chlorophyll a and carotenoids by ۲۳.۸% and ۵۷.۶%, respectively, compared with the control, and significantly increased antioxidant enzyme activities, particularly superoxide dismutase (SOD) and catalase (CAT). Similarly, at moderate salinity levels (۶۰–۱۲۰ mM), ۲۵۰ μM melatonin maintained high enzyme activity and improved potassium retention. However, under severe salinity (۱۸۰ mM NaCl), ۱۵۰ μM melatonin was more effective in maintaining water balance, reducing ion leakage by up to ۲۰%, lowering MDA by ۳۱%, and decreasing Na+ accumulation by up to ۵۳%. The shift in optimal concentration from ۲۵۰ μM under non-saline or mild stress to ۱۵۰ μM under severe stress reflects the plant’s adaptive regulation, where higher melatonin enhances growth under optimal conditions, whereas moderate levels suffice to activate antioxidant defenses and maintain ionic balance under stress. Overall, melatonin within the ۱۵۰ –۲۵۰ μM range effectively enhanced antioxidant activity, ionic homeostasis, and salinity tolerance in R. damascene.

کلیدواژه ها:

Antioxidant enzymes ، Carotenoids ، Electrolyte leakage ، Lipid peroxidation ، Proline ، Antioxidant enzymes ، Carotenoids ، Electrolyte leakage ، Lipid peroxidation ، Proline