Evaluation of glycyrrhizin contents in licorice (Glycyrrhiza glabra L.) under drought and soil salinity conditions using nutrient concentrations and biochemical traits as biomarkers

Abstract

Drought and salinity limit crop yields throughout the world, and understanding the plant response mechanisms to these stresses can provide new insights into how to breed stress-tolerant genotypes. The leaf and root responses of five different licorice (Glycyrrhiza glabra) genotypes to drought and salinity stresses were investigated in field conditions, using control conditions and five stress levels (slight, moderate and intense drought; moderate and intense salinity). Parameters measured include leaf and root macronutrient concentrations, leaf photosynthetic pigment concentrations, leaf and root total antioxidant and phenolic compound concentrations and root concentrations of the secondary metabolites glycyrrhizin and glabridin. Drought and salt stresses caused progressive decreases in leaf photosynthetic pigment concentrations, accompanied by major changes in macronutrient concentrations in leaves (including increases in Na, Cl, K and Ca and decreases in Mg) and roots (including increases in Na and Cl, and decreases in K, Ca and Mg). Increases in leaf antioxidant enzyme activities (CAT and APX), leaf and root total antioxidant activity and total phenolics were also observed with both stresses. Multiple regression analysis suggest that it could be possible to make a fair estimation of the root glycyrrhizin concentrations using parameters that can be measured more easily, such as the leaf concentrations of macronutrients and photosynthetic pigments.