Effect of GA₃ and Environmental Factors on Seed Germination Rates of Hypericum perforatum L.

This study aimed to evaluate the effects of gibberellic acid (GA₃) on the germination of Hypericum perforatum (St. John's Wort) seeds. The first trial tested three GA₃ concentrations (200, 300, 400 mg·L⁻¹) and three incubation durations (24, 72, 120 hours) under dark conditions. The second trial focused on the interaction of GA₃, temperature (15, 25, 35°C), and photoperiod conditions. As a result, GA₃ significantly improves germination rates, with concentrations of 200–300 mg·L⁻¹ and treatment durations of 72–120 hours being the most effective. Temperature and light conditions were also found to be critical, with the optimal temperature for germination being 15°C. At higher temperatures, particularly 35°C, germination was either minimal or absent. Light exposure under a 16/8-hour photoperiod led to significantly better germination compared to continuous darkness. The highest germination rates (up to 96.75%) were observed under a combination of 200 mg·L⁻¹ GA₃ and light exposure at 15°C. This study highlights the synergistic effect of GA₃ and light, which together enhanced germination success.