Study the Antioxidant Enzymes’ Activity and Biochemical Responses of Safflower as Affected by Foliar Application of Melatonin under Drought Condition

In order to study the foliar application of melatonin on plants grown from safflower in different seed qualities under drought condition, two field experiments have been carried out at research farm of Aburaihan Campus, University of Tehran, between 2017 and 2018 growing seasons. The experimental design is split-factorial in a randomized complete block design with four replicates, with the treatments being consisted of two levels of drought stress (1- normal irrigation (no-stress) and 2- irrigation after reaching 85% of soil moisture depletion of field capacity at flowering stage (drought stress)), in the main plots. The subplots include 4 treatments, including a factorial combination of seed quality (stored seed and recently harvested seeds) and foliar application (the control and melatonin foliar application). Results from these experiments illustrate that melatonin foliar application has significantly increased the seed yield of stored seed by 589Kg.ha-1, compared to the control. It is also shown that SOD and CAT activities have been increased in response to melatonin in plants grown from recently-harvested seeds under drought condition. Furthermore, it is indicated that foliar application of melatonin decrease the amount of leaf soluble proteins by 28% in plants grown from recently-harvested seeds under drought conditions. According to the results, the amount of malondialdehyde is decreased by 37% in plants grown from recently-harvested seeds by foliar application of melatonin under drought conditions. It seems that seed quality has an enormous influence on grown plants and that using melatonin may play a substantial role in ameliorating the injuries derived from stress on safflower plant.