Effect of Exogenous ALA on Seed Germination and Physiological Characteristics of Glycyrrhiza uralensisSeedlings under Drought Stress

In order to get the method of improve the drought resistance of seeds and seedlings for Glycyrrhiza uralensis under drought stress,we studied seed germination and physiological characteristics of G.uralensis seedlings.Several physiological indexes of G.uralensis seeds were measured treated by 5-aminolevulinic acid(ALA) under drough stress like the germination vigor,germination rate,germination index and vigor index.And other indexes of the seedlings like the membrance permeability,the contents of malondialdehyde(MDA),soluble sugar and proline,the activities of superoxide(SOD),peroxidase(POD) and catalase(CAT) were also measured.The result shows:(1)the germination indexes of G.uralensis seeds under drought stress have a obvious inhibition.But after the treatment of different concentrations of ALA,every germination indexes were all increased.And the seeds that treated by ALA with the concentration of 10 mg·L-1 has the most significantly increase.The germination vigor and the germination rate was 75% and 91%,respectively,compared with the drought stress,it improve 35% and 30%,respectively.The germination indexes and vigor index were 36.2 and 709.7,respectively.It is 2.6 and 3.5 times to the drought sress.(2)Every treatments were all improved the biomass of the seedlings,the contents of soluble sugar(37.20 mg·g-1) and proline(28.79 μg·g-1) increased significantly compared to the drought stress.But after treated by ALA,the content of MDA(10.42 μmol·g-1) decreased under drought stress and the rate of decrease has been relieved.The membrance permeability was also decreased to 8.44%.The activities of three enzymes include SOD,POD and CAT were all increased.And the treatment of ALA with the concentration of 10 mg·L-1 get the maximin with 882.84 U·g-1·h-1,27.63 U·mg-1·min-1 and 3.45 U·mg-1·min-1,respectively.These result show that ALA with the appropriate concentration of 10 mg·L-1 could significantly alleviate the damages to the seeds and seedlings of G.uralensis under drought stress and promote the drought resistance of the seeds and seedlings.