Effect of gibberellin cacid hormone and mother corm weight on vegetative and reproductive growth of saffron (Crocus sativus L.)

Saffron is one of the most important crops and medicinal plants in Iran and plays an important role in non-oil exports of the country. Saffron is cultivated in most part of Iran, because of low water requirement and well adaptation to diverse environmental condition. Therefore, the present study is to investigate the effects of corm weights and gibberellic acid on yield and vegetative characteristics of saffron. The effects of applications of gibberellic acid hormone (GA) and mother weight corm on flower yield and growth characteristics 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. The measured indices were included of leaf characteristics (leaf length, fresh and dry weight, chlorophyll a, b and total leaf) and flower characteristics (flower number and fresh total yield, average stigma length, stigma fresh and dry yield). The results indicated that mother corm weight had significant effect on all flowering traits, so that the highest flowers number, flower yield (37.7% per m2,6.59 g. m-2), flowers fresh weight and stigma fresh weight (0.381 g, and 0.025) was observed from corm weight 8.1-12 g and the least of them was recorded from corm weight 0.1-4 g. Also, with increase corm weight, increased the leaf traits (leaf length, leaf weight, chlorophyll a, b and total leaf), so that the highest and lowest of these traits were recorded with corm weight 8.1-12 g and 0.1-4 g, respectively. It was found that gibberellic acid had significant effect on most vegetative traits of leaves, so that the highest leaf length (32.02 cm), leaf number (28.26), Leaf fresh weight (0.388 g), chlorophyll a (0.203 mg. g) were obtained from gibberellic acid treatment. but, gibberellic acid reduced the number of flowers. Also, interaction effects of gibberellic acid and corm weight had a significant effect on chlorophyll b and stigma length. According to this study, results showed that corm weight (12-8/1 g) had strong impact on growth characteristics and yield of saffron, increased saffron vegetative and reproductive characteristics, while, the use of gibberellic acid only improved the vegetative traits and didn't affect on saffron flowering traits