Effect of PEG-simulated Drought Stress on Seed Germination of Three Medicinal Liquorice (Glycyrrhiza) Species

Background: Glycyrrhiza is an important medicinal plant that has been in shortage in recent years because of high demand and exhaustive harvesting. Investigating the drought tolerance of liquorice species can inform the artificial cultivation of liquorice under different water conditions and help address the shortage.Methods: Seeds of G. uralensis, G. glabra and G. inflata were treated with different concentrations of polyethylene glycol (PEG)-6000 solutions to simulate different levels of drought stress. The germination process germination rate, germination index, vigour index, stress tolerance index and recovery germination percentage of seeds were measured. Drought tolerance was evaluated using the membership function.Result: Low concentrations of PEG promoted the seed germination of G. glabra and G. inflata, whereas high concentrations inhibited the seed germination of all three plants. The degree of inhibition increased with increasing PEG concentration. Under mild PEG stress, the drought tolerance of G. uralensis was highest and that of G. glabra was the lowest. However, under severe PEG stress, the drought tolerance of G. glabra was the highest and that of G. uralensis was the lowest. Therefore, seeds of G. uralensis should be sown in relatively moist soil and those of G. glabra in relatively arid soil.