Effect of day length and gibberrelic acid on some morphological and biochemical ‎characteristics of chrysanthemum

In order to accelerate the flowering time in four late flowering chrysanthemum cultivars, the effect of different concentrations of gibberellic acid and day length on flowering time and some quantitative and qualitative characteristics, an experiment was conducted as a factorial split plot in a completely randomized design with three treatments and four replications. Cultivars included Ariamanesh, Roxana, Dina and Oran. Gibberellic acid treatment at four levels (0, 75, 150 and 300 mg/ l) and foliar application time at two levels (30 and 45 days after transplanting) were applied. Daytime treatments at three levels included 16 hours of light - 8 hours of darkness (control), 12 hours of light - 12 hours of darkness and 8 hours of light - 16 hours of darkness. In this experiment, the main and sub plots were day length and gibberellic acid, respectively. The studied traits included flowering stem length, flower number, flower diameter, dry weight of flowers and leaves, content of photosynthetic pigments, peroxidase and number of days to flowering. The results showed that the highest flower number, diameter and dry weight of flowers were obtained in the treatment of 300 mg/l gibberellic acid and 16 hours of darkness. Flowering time was accelerated by 300 mg/l gibberellic acid and 16 hours in the dark compared to the control for about 21 days. Dina cultivar was also recognized as the best cultivar in response to different levels of gibberellic acid and reduction in day length, so that the number of days to flowering in this cultivar compared to other cultivars showed a significant decrease.