Abstract
Two-year-old seedlings of licorice plant (Glycyrrhiza uralensis Fisch) were exposed to three degrees of water deficit, namely weak (60-70%), moderate (40-50%), and strong (20-30%) relative water content in soil, whereas control plants were grown in soil with 80-90% water content. Moderate and strong water deficit decreased the net photosynthetic rate, stomatal conductance, and biomass production. Water use efficiency and the root-to-shoot ratio increased significantly in response to water deficit, indicating a high tolerance to drought. Weak water deficit did not decrease root biomass production, but significantly increased the production of glycyrrhizic acid (by 89%) and liquiritin (by 125%) in the roots. Therefore, a weak water deficit can increase the yield of root medical compounds without negative effect on root growth.