Journal of Plant Process and Function

Considering low vigor of Stevia (Stevia rebaudiana Bertoni) seeds and difficulty of its germination, the purpose of this experiment was to evaluating the effect of different priming types on germination and seedling growth of Stevia in the presence of gibberellic acid. A factorial experiment was carried out based on a completely randomized design with three replications. Treatments consisted of different concentrations of gibberellic acid (G1=0, G2 =25 and G3=50 mg L^-1) and seed priming as hydro, hormone (gibberellic acid, 0.2 mg L^-1) and Osmo (3% potassium nitrate) for 18 hours. The essential oil constituents were measured by gas chromatography (GC). The activity of hydrolytic and antioxidant enzymes in seedlings also were measured. The highest germination percentage (67.26 %) observed in the hormone priming and the concentration of 50 mg L^-1 of gibberellic acid. Osmopriming had the highest germination rate. The highest levels of SOD activity and MDA content observed in osmopriming and catalase and peroxidase achieved in hydro priming without application of gibberellic acid. The highest level of alpha-amylase enzyme activity was related to hormone priming with 50 mg L^-1 gibberellic acid. The highest levels of alphacadinol, methyl salicylate and Safranal and also carbohydrates and protein observed in hormone priming and 50 mg L^-1 gibberellic acid. In conclusion, to achieve the highest essential oil contents in Stevia using hormone priming and application of 50 mg L^-1 gibberellic acid was suitable.