Effect of Melatonin and Sodium Nitroprusside Foliar Application on Improving High-Temperature Stress Tolerance of 'Kurdistan' Strawberry

An experiment was conducted to examine whether the foliar application of melatonin (MA) and nitric oxide (NO) would improve thermo-tolerance of strawberry plants subjected to high-temperature stress. For this purpose, a factorial experiment in a completely randomized design with three replications, in the college of Agriculture, Isfahan University of Technology was performed. The strawberry plants cv. Kurdistan were exposed to various temperatures (25, 35, and 40 °Ϲ) for 24 hours after pre-treatment with 0, 50, and 100 μM MA and NO. Heat stress significantly induced hydrogen peroxide and malondialdehyde content and increased proline accumulation, whereas reduced relative water content (RWC) and the maximal efficiency of PSII photochemistry (Fv/Fm). In addition, heat stress increased glutathione and ascorbic acid contents and enhanced superoxide dismutase and guaiacol peroxidase activities, and reduced catalase and ascorbate peroxidase activities. Treatment with MA and NO decreased heat injury symptoms and induced antioxidant enzyme systems and increased non-enzymatic antioxidant contents. Melatonin and NO increased proline content, RWC, and improved Fv/Fm compared with the non-treated plants. These results suggested that in strawberry, MA and NO alleviate heat-induced oxidative damage by modulating antioxidant pathways, decreasing reactive oxygen species, and inhibiting lipid peroxidation.