Effects of different gibberellic acid levels and corm weight on antioxidant activity and secondary metabolites of saffron (Crocus sativus L.)

The effects of applications of gibberellic acid hormone (GA) and mother weight corm on antioxidant activities and components of saffron were evaluated under field conditions. Treatments were tow levels of gibberellic acid (0 and 20 ppm) and three mother corm weights (0.1- 4, 4.1- 8 and 8.1- 12 g).The experiment was designed as factorial arrangement based on randomized complete block design with three replications at the Research station of Faculty of Agriculture University of Birjand during growing season of 2016-2017.Traits including antioxidant activity, anthocyanins, phenols, crocin, picrocrocin and safranal of saffron. The results indicated that treatments had significant effect on antioxidant activity of stigma and petals. The highest antioxidant activity (39.5%) was found in gibberellic acid, but corm weight had no effect on this trait. Also, the highest anthocyanins (Stigma and Petal) was recorded from corm weight 8.1-12 g (1.31 and 0.96 mg / 100 g dry weight) and the lowest was obtained from corm weight 0.1-4 g (1.039 and 0.679 mg/100 g dry weight, respectively). Although, gibberellic acid treatment had no effect on the anthocyanins of petal. Total phenol increased with the use of gibberellic acid, the highest phenol (0.627 mg /100 g dry weight) was obtained from corm weight 8.1-12 g and the lowest was obtained from corms weight 0.1-4 g. The highest levels of safranal (32.56 %) and picrocrin (58.19%) were observed from gibberellic acid treatment. Also, the interaction between gibberellic acid and corm weight was significant on crocin content .The highest crocin (152.6%) was obtained from corm weight of 8.1-12 g and gibberellic acid. The beneficial effects of the use of gibberellic acid and high corm weight on the improvement of biochemical traits and effective saffron substances