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.

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