Effects of growth regulators on pomegranate (Punica granatume L. cv. Rabab) fruit quality under drought stress condition

Water availability, especially in arid regiones, is one of the major constraints for achieving optimum growth yield. In recent years, several numbers of researches has been done with different methods on adapting plants to environmental stresses such as drought stress. In this experiment, two plant growth regulators named 24-epibrassinolide and Jasmonic acid was used to improve drought tolerance of pomegranates (Punica granatume L. cv. rabab). Treatments were three levels of irrigation included sufficient water (control), mild stress (75 % of field capacity) and moderate stress (50 % of field capacity) and 9 levels of hormones included control (water), 24-epibrassinolide (0.1 and 0.2 mg/l), jasmonic acid (1 and 2 mg/l) and their combinations. These treatments arranged in factorial experiment in the form of complete randomized block design with four replications. Plant growth regulators sprayed on the leave of fertile trees before flowering and after fruiting rapid growth. Results showed that many chemical and biochemical parameters of fruit affected by drought stress. Application of 24-epibrassinolide and Jasmunic acid growth regulators changed the amount of total phenols in peel and fruit juice. The amount of antioxidant activity in peel and fruit juice was also altered by the above mentioned plant regulators. Results also showed that application of 0.2 mg/lit of 24-epibrassinolide in combination with 2 mg/lit of jasmunic acid could ameliorate antioxidant activity in peel under control and drought stress conditions. Application of 2 mg/lit of Jasmunic acid ameliorated the activity of peroxidise enzyme in fruit juice severe drought stress. According to the results, application of Jasmunic acid, lonely, or in combination with 24-epibrassinolide could have a positive effect on antioxidant activity of pomegranate fruit under the mentioned concentrations.