Effects of different plant growth regulators on seed germination and seedling growth of Origanum vulgare

This study aimed to screen suitable plant growth regulators and their optimal concentration to promote the seed germination and seedling growth of Origanum vulgare. The effects of different concentrations of GA₃ (100, 200, 300, 400, 500 mg·L⁻¹), 6-BA (20, 40, 60, 80, 100 mg·L⁻¹) and NAA (30, 60, 90, 120, 150 mg·L⁻¹) on seed germination and seedling growth of O. vulgare were studied by Petri dish germination method. The results show that GA₃ at concentrations of 100～400 mg·L⁻¹, 6-BA at 20 mg·L⁻¹, and NAA at 30～120 mg·L⁻¹ can significantly improve germination capacity (P < 0.05). Among them, soaking with 300 mg·L⁻¹ of GA₃ had the best effect; the germination rate increased from 52.00% to 90.67%, the germination potential increased from 42.00% to 72.00%, the germination index increased from 9.60 to 14.97, and the vigor index increased from 188.34 to 360.40. However, soaking seeds with 100 mg·L⁻¹ 6-BA could inhibit the germination of O. vulgare. Three kinds of plant growth regulators had different effects on the growth of O. vulgare. Soaking seeds with GA₃ of 300 mg·L⁻¹ was beneficial to the accumulation of seedling biomass, while soaking with 20 mg·L⁻¹ 6-BA was beneficial to the elongation of the radicle of O. vulgare; soaking seeds with 60 mg·L⁻¹ NAA significantly promoted the elongation of the hypocotyl of O. vulgare. Physicochemical analysis found that the effects of three plant growth regulators at different concentrations on soluble protein and antioxidant enzymatic activities of O. vulgare show a trend of first increasing and then decreasing. In conclusion, soaking with 300 mg·L⁻¹ GA₃, 20 mg·L⁻¹ 6-BA, and 60 mg·L⁻¹ NAA were the optimum concentrations for seed germination of O. vulgare which could effectively improve seed germination and seedling growth.