mahnaz karimi - Assistant professor, Department of Horticultural Sciences, Faculty of crop Sciences, Sari Agricultural Sciences and Natural Resources University, Sari
masomeh mohamadi - MSc student, Department of Horticultural Sciences, Faculty of crop Sciences, Sari Agricultural Sciences and Natural Resources University

Melatonin is a new plant hormone that plays an important role in stress tolerance. For investigation the effect of exogenous application of melatonin on salt tolerance in rosemary (Rosmarinus officinalis L.), a factorial experiment was conducted in a completely randomized design with three replications. The first factor was melatonin (۵۰, ۱۰۰ µM) and the second factor was salinity stress (۶, ۹, ۱۲ ds m-۱). Water was used for control treatment. In the treated plants with concentrations of ۶, ۹ and ۱۲ dsm-۱ NaCl, stem height decreased compared to the control. Melatonin treatment (۱۰۰ μM) reduced the effects of NaCl stress. ۱۰۰ μM melatonin increased leaf growth compared to the control. The highest activity of SOD and POD was recorded in pretreatment plants with ۵۰ and ۱۰۰ μM melatonin. Melatonin prevented the reduction of chlorophyll content due to salt stress. The lowest ion leakage was related to ۱۰۰ μM melatonin in control, ۶ and ۹ dsm-۱ NaCl. Also, the highest reduction of electrolyte leakage (with ۲۸.۵% reduction) was related to ۱۰۰ μM MT at ۱۲ dsm-۱NaCl. According to the results, ۱۰۰ μM melatonin was more effective in reducing the effects of salinity stress.

Antioxidants, Electrolyte leakage. Oxidative damage, plant development, Salt tolerance