Important changes in germination, seedling tolerance, and active components content due to drought stress on three licorice (Glycyrrhiza) species

Drought stress triggers complex physiological and biochemical responses in plants. Different plant species have also evolved several morphological, physiological, biochemical, cellular, and molecular mechanisms to overcome drought stress conditions. However, genotype-specific response factors associated with drought tolerance and the balanced relationship between active components and stress conditions are still not fully elucidated. Licorice (Glycyrrhiza Tourn. L.) is a perennial herb of the Leguminosae family which is widely used as a spice in the food industry. It is favored for its sweet and distinctive aromatic flavor, which is attributed to its glycyrrhizic acid, liquiritin, and other components. The influence of drought stress on different species of licorice was analyzed. Seed germination parameters, the activity of anti-oxidative enzymes, osmoregulation, and active compound contents were compared in three licorice species (Glycyrrhiza glabra L., Glycyrrhiza uralensis Fisch., and Glycyrrhiza inflata Bat.). The results indicated a level of drought stress that balanced relatively good growth trends and high expression of active compounds in individual licorice species. With increasing drought stress, G. uralensis and G. glabra had lower values of early germination indicators (germination energy, germination rate, and germination index), when compared to G. inflata. The highest values of antioxidant enzyme activity and active compound content were detected at lower stress levels in both G. uralensis and G. glabra. The active components (glycyrrhizic acid, liquiritin, isoliquiritin, liquiritigenin, isoliquiritigenin, 4′,7-dihydroxyflavone, and licochalcone A) showed significantly different trends in different species under drought stress. The current study will help understand the effects of drought stress on licorice plants. The results highlight the importance of preserving regional genetic diversity for adaptive evolution in response to global climate change. It also provides a theoretical basis for revealing rational cropping regions and formulating adaptive irrigation strategies.