Study on the Characteristics of Growth, Yield, and Pharmacological Composition of Licorice (Glycyrrhiza uralensis Fisch.) in a Temperature Gradient Tunnel

Background: Studies have suggested that the northern provinces of Gangwon-do are good sites for licorice (Glycyrrhiza uralensis Fisch.) cultivation in Korea, as they have similar temperatures to its original locations in northern China. However, poor growth and freezing injury are often reported in Korea. Therefore, it is necessary to reassess the domestic cultivation site of licorice.BR Methods and Results: To determine the optimum temperature for cultivating licorice, the growth, yield, and pharmacological characteristics of G. uralensis were assessed in a temperature gradient tunnel at Eumseong, Chungcheongbuk-do, Korea in 2017. Plant height increased until the temperature rose to 5.9℃ above the local external temperature. Yield (㎏/10a) increased by 46.9% when the growing temperature was 1.5℃ to 3.0℃ (T2) above the external temperature and by 72.6% when the growing temperature was 3.0℃ - 4.5℃ (T3) above the external temperature. However, a difference of 4.5℃ - 5.9℃ (T4) above the external temperature, decreased the yield by 9.8% compared to that at T2. The glycyrrhizin content of G. uralensis roots in each temperature band was 0.72%, 0.53%, 0.91%, and 0.84% (T1, T2, T3, T4), these differences appear to result form individual plant variation rather than growth temperature.BR Conclusions: Based on the results of this study, we estimate that the temperature-based optimum cultivation site for G. uralensis in Korea is the south central region, rather than the northern province of Gangwon-do. Improvement in growth and yield maybe observed if the plantations in the central Jecheon (Chungcheongbuk-do, Korea) are expanded into the south central region.