Effects of Drought Stress and Rehydration on Physiological Characteristics and Glycyrrhizin Accumulation of Glycyrrhiza uralensis Fisch.Seedling

Potted Glycyrrhiza uralensis Fisch.seedlings were subjected to progressive drought stress by stopping watering for 0 d,3 d,6 d,9 d,12 d,and rehydration for 3 d on the 6th and 12th days under drought stress.The changes of some physiological indexes of leaves and the glycyrrhizin content in roots were investigated.The results showed that,with prolonging of drought stress time,the malondialdehyde(MDA) content,and the activities of SOD and POD increased significantly,the glycyrrhizin content kept on increasing,the leaf relative water content(RWC) increased on the third day and then decreased significantly,the activity of APX increased remarkably on the 9th and 12th days,the activity of CAT and the content of soluble protein increased significantly at first and then decreased remarkably,the proline content increased significantly from the 6th day,and the content of soluble sugar increased firstly and then became lower and then increased at last.The RWC of both R6(rehydration at the 6th day under drought stress) and R12(rehydration at the 12th day under drought stress) recovered to the level of 0 d.Compared with D6(the 6th day under drought stress),the contents of R6's glycyrrhizin,proline,and soluble protein increased significantly,the contents of MDA and soluble sugar,and the activity of POD decreased remarkably,the activities of SOD,CAT and APX became much higher.Compared with D12(the 12th day of drought stress),the contents of R12's glycyrrhizin,MDA,proline,and soluble sugar decreased significantly,the activities of POD and APX became much lower,and the activity of CAT became much higher.Both the content of soluble protein and the activity of SOD were not significantly different between D12 and R12.Above results suggested that Glycyrrhiza uralensis Fisch.Seedling had strong drought resistance,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.