Effect of gibberellic acid treatment and alternating temperature on breaking physiological dormancy and germination in Penthorum chinense Pursh (Penthoraceae)

Penthorum chinense (Penthoraceae) is a threatened South Korean medicinal plant used to treat alcohol-related diseases and prepare cosmetics in traditional Chinese medicine. Wetlands, the native habitat of this plant, have been decreasing owing to damage caused by landisation and urban development in recent years. In this study, we considered the effect of temperature and gibberellic acid treatment on P. chinense seed germination to improve conservation outcomes of the species. The optimum germination temperature was investigated using constant and alternating temperature treatments (60 conditions). In addition, gibberellic acid (GA3) treatment was performed to overcome physiological dormancy. We determined the germination (GP, %) and the number of days to reach 50% maximum germination (T50). The optimum temperature regime was 7°C / 23°C: GP was 95%, and T50 was 15 days. The GA3 treatment increased the GP of P. chinense seeds from 28 to 94% and decreased the T50 value from 14.6 to 6.3 days at concentrations above 40 mg L-1. After the GA3 treatment, the growth of radicles was delayed or inhibited. For the germination of P. chinense seeds, a diurnal temperature difference of ≥ 15°C is required.