The effect of different treatments on the breaking seed dormancy of Stevia rebudiana

Stevia is an important natural sweetener in the world, which this issue has led to more demand for stevia production. In order to investigate various breaking dormancy treatments on stevia seeds this study was conducted as a factorial experiment based on the completely randomized design with three replications and two factors in the research laboratory of Shahid Bahonar University of Kerman in 2021. The factors were included gibberellic acid in three levels (0, 0.5 and 1 mM) and temperature treatment (control, warm water, liquid nitrogen, wet cooling treatment for seven days, wet cooling treatment for 14 days, dry cooling treatment for seven days and dry cooling treatment for 14 days). The results showed that the effect of temperature and gibberellic acid treatments on germination characteristics of stevia was significant at the probability level of 1%. Among the studied treatments, the interaction of dry cooling and 1% gibberellic acid was the most effective treatment, and the highest germination percentage (74.01%) and germination speed (14.15 seed day-1) belonged to the mentioned treatment. The results of mean comparisons showed that the effect of gibberellic acid application led to a significant increase in hydrogen peroxide, alpha-amylase, protease and dehydrogenase traits compared to the control. Therefore, it can be stated that dry cooling treatment with 1% gibberellic acid can be effective in improving germination characteristics in stevia plant.