Effects Of Drought And Hormones On Physiological Characteristics And Glycyrrhizin Accumulation Of Glycyrrhiza Uralensis Fisch.

With potted annual Glycyrrhiza uralensis Fisch. seedlings as experimental material, artificially controlling soil moisture content, the changes of physiological indexes and the glycyrrhizin content were investigated under the treatment of drought stress and rehydration and foliar spraying methyl jasmonate(MeJA) and gibberellin(GA₃) respectively, which is in order to provide some theoretical basis for high-yield and water-saving culture, and provide some theoretical reference for the research of revealing the mechanism of glycyrrhizin biosynthesis and the role of glycyrrhizin in licorice adapting to arid environment.The results of the experiment of drought stress and rehydration showed that, annual Glycyrrhiza uralensis Fisch. seedlings had strong drought resistance, antioxidant protective enzyme system including superoxide dismutase(SOD), peroxidase(POD), catalase(CAT) and ascorbate(APX) cooperate with each other to mitigate reactive oxygen damage, and the osmoregulation substance contents of proline, soluble protein and soluble sugar increased to maintain cell turgor pressure. And short-term rehydration after moderate drought stress increased the accumulation of glycyrrhizin, and enhanced the ability of drought resistance of Glycyrrhiza uralensis Fisch. seedling. With drought stress aggravating and sustaining, the glycyrrhizin content kept on increasing, ratio of shoot/root increased, the leaf relative water content increased and then decreased significantly, the superoxide anion radical(O2·-) content, malonaldehyde(MDA) content, and the acitivities of SOD and POD increased significantly, the activity of CAT and the content of soluble protein increased significantly first and then decreased remarkably, the activity of APX increased significantly under severe drought stress, the proline content increased remarkably under moderate and severe drought stress, and the content of soluble sugar increased first and then became lower and then increased at last. The leaf relative water content recovered to the level of normal water supply when rehydration after moderate and severe drought stress. Comparing with moderate drought stress, the ratio of shoot/root increased when rehydration after moderate drought stress, the contents of glycyrrhizin, O₂·-, proline and soluble protein and the activities of SOD, CAT and APX increased significantly, the contents of MDA and soluble sugar and the activity of POD decreased remarkably. Comparing with severe drought stress, the ratio of shoot/root decreased when rehydration after severe drought stress, the contents of glycyrrhizin, O₂·-, MDA, proline and soluble sugar and the activities of POD and APX decreased significantly, CAT activity increased remarkably, soluble protein content and SOD activity had no significant difference.The results of the experiment that foliar spraying MeJA and GA₃ on Glycyrrhiza uralensis Fisch. seedlings under moderate drought stress showed that, exogenous spraying MeJA enhanced drought resistance of Glycyrrhiza uralensis Fisch. seedlings, increased the accumulation of glycyrrhizin, the effects of 0.5mmol·L^-1 MeJA treatment were the best; exogenous spraying GA₃ promoted primary metabolism, and the lower concentration of GA₃ treatment increased the biomasses of both shoot and root, and decreased the accumulation of glycyrrhizin. Foliar spraying MeJA increased the ratio of shoot/root under moderater drought stress, glycyrrhizin content of each plant decreased significantly under 0.01mmol·L^-1 and 1mmol·L^-1 MeJA treatment, and increased significantly under 0.05mmol·L^-1, 0.1mmol·L^-1 and 0.5mmol·L^-1 MeJA treatment; the leaf relative water content, and the activities of POD and APX had no significant difference, the contents of O₂·-, soluble protein and soluble sugar, and SOD activity decreased remarkably; MDA content decreased remarkably under 0.05mmol·L^-1 and 0.1mmol·L^-1 MeJA treatment, and had no significant difference under 0.01mmol·L^-1, 0.5 mmol·L^-1 and 1mmol·L^-1 MeJA treatment; CAT activity under 0.01mmol·L^-1 MeJA treatment had no significant difference, and decreased remarkably under 0.05mmol·L^-1, 0.1mmol·L^-1, 0.5mmol·L^-1 and 1mmol·L^-1 MeJA treatment; proline content under 0.5mmol·L^-1 and 1mmol·L^-1 MeJA treatment had no significant difference, and decreased remarkably under 0.01mmol·L^-1, 0.05mmol·L^-1 and 0.1mmol·L^-1 MeJA treatment. Foliar spraying GA₃ decreased the ratio of shoot/root, leaf relative water cntent, O₂·- content and soluble protein under moderate drought stress, glycyrrhizin content of each plant decreased significantly, the contents of MDA and soluble sugar increased remarkably, SOD activity had no significant difference; POD activity under 100mg·L^-1 and 500mg·L^-1 GA₃ treatment had no significant difference, and increased significantly under 25mg·L^-1, 50mg·L^-1 and 300mg·L^-1 GA₃ treatment; APX activity under 300mg·L^-1 GA₃ treatment had no significant difference, and increased remarkably under 25mg·L^-1, 50mg·L^-1, 100mg·L^-1 and 500mg·L^-1 GA₃ treatment; proline content under 500mg·L^-1 GA₃ treatment had no significant difference, and increased remarkably under 25mg·L^-1, 50mg·L^-1, 100mg·L^-1 and 300mg·L^-1 GA₃ treatment.