Effects of gibberellic acid and naphthalene acetic acid on saffron plant (Crocus sativus L.) under field conditions

An experiment was conducted to investigate the effect of growth regulator treatments on quantitative and qualitative yield of saffron. Growth regulator treatments included 50, 150 and 300 ppm gibberellic acid (GA3) and naphthalene acetic acid (NAA) . Saffron corms weighing 8 to 10 g were immersed in solutions of GA3 and NAA and then were planted in 1×1 meter plots with 15 cm within row and 20 cm between row spacing. At the end of the growing season (end of June), crop traits such as total number and weight of the produced corms and the number and weight of produced corms in weighing groups of less than 4 g, 4 to 8 g, and more than 8 g were measured by harvesting one third of the cultivated corms in each plot. At the flowering time of the remaining corms of each plot (November), weight and number of flower, fresh and dry weight of stigma, and the amount of active ingredients including crocin, picrocrocin and safranal were measured. The results showed that all studied traits were affected by growth regulator compounds and indicated significant (P≤0.01 and P≤0.05) differences with control. GA3 improved biological yield and corm weight, in addition it could increase the quality of stigma compared to the control treatment. Application of 150 ppm GA3 increased the weight of corms by 16.25 % and the number of flower plot-1 by 34.99 % compared to the control treatment. Also, 300 ppm GA3 increased the dry stigma yield by 37.5 % compared to the control treatment. NAA did not affect yield production significantly and at high concentrations, prevented the growth of corms and flower production. Results indicated that concentrations higher than 150 ppm GA3 can increase the yield of saffron, and can play an important role in enhancement of saffron farms productivity.