Objective: Licorice (Glycyrrhiza glabra L.) seed propagation is constrained by a hard seed coat and slow, non-uniform germination. This study evaluated the effects of chemical treatments, light, and temperature on germination, seedling vigor, and early growth of licorice.
Method: Five independent experiments were conducted: sulfuric acid (50% and 98% for 30 and 60 min), gibberellic acid (50, 100, and 200 mg L⁻¹ for 24, 48, and 72 h), potassium nitrate (0.2%, 0.4%, and 0.6%), light quality (red, blue, white, 70% red + 30% blue, far-red, and darkness), and temperature regimes (constant 4, 11, and 25 °C, plus a boiling-water pretreatment). Each experiment used a completely randomized design with four replicates of 20 seeds. Germination, seedling growth, and vigor traits were measured.
Results: Treatment effects were significant for most traits. Sulfuric acid (98%, 30 min) gave 100% germination and the highest germination rate (13.45 seeds day⁻¹), while 60 min produced the greatest seedling length and vigor index. Gibberellic acid at 100 mg L⁻¹ for 72 h gave the highest vigor index, and 200 mg L⁻¹ for 72 h the highest germination rate. Potassium nitrate at 0.6% gave the highest germination percentage and rate, while 0.4% improved seedling growth and vigor. Blue light enhanced germination percentage and speed, whereas darkness increased seedling length, fresh weight, and vigor index. Boiling water followed by 25 °C gave the highest germination percentage and rate, while continuous 11 °C produced the greatest seedling length and numerically highest vigor index.
Conclusions: Licorice seed responses depended on both treatment type and trait evaluated, so treatments maximizing germination did not necessarily produce the most vigorous seedlings. Treatment selection should therefore consider both germination and seedling quality. These findings provide a practical basis for improving licorice propagation and for designing greenhouse and field validation studies.
