Effects of PEG-6000 simulated drought stress on seed germination of Astragalus

In order to screen out the germplasm materials of Astragalus with strong drought resistance, different concentrations（5%,10%,15%,20%）of polyethylene glycol（PEG-6000） were used in this study to simulate drought stress germination test on the seeds of 6 Astragalus（from No.1 to No.6:Astragalus purdomii,A. adsurgens Pall.cv.zhongsha No.1, A. adsurgens Pall.cv.chunjiang No.1, Astragalus adsurgens Pall., Astragalus laxmannii, Astragalus herb）. The purified water without PEG-6000 was used as control. The root length and plumule length of seeds were measured and the germination rate, germination potential, germination index, vitality index, relative germination percentage, relative germination potential, relative germination index, relative vigor index, RL/PL, relative bud length and relative root length were calculated under drought stress treatment. Fuzzy mathematics membership function method was used for comprehensive evaluation. The results showed that the seed germination of the same breed was different under different PEG-6000 concentrations of stress. The germination rate, germination potential, germination index, and vitality index of No.1（Astragalus purdomii） were higher than those in the control when PEG-6000 stress concentrations were 5%, 10%, and 20%. The germination rate, relative root length, and RL/PL of No.6（Astragalus herb） were higher than those in the control at a PEG-6000 stress concentration of 15%, which could promote seed germination. The germination potential, germination index, and vitality index of No.2（A. adsurgens Pall.cv.zhongsha No.1） and No.5（Astragalus laxmannii） were lower than those in the control under the various concentrations of stress, and their seed germination was inhibited. There were no significant changes in the germination potential, germination index, and vitality index of No.3（A. adsurgens Pall.cv.chunjiang No.1） and No.4（Astragalus adsurgens Pall.）. The seed germination of different breed was different under the same concentration of drought stress.The germination rate, germination potential, germination index, and vitality index of No.1（Astragalus purdomii） and No.6（Astragalus herb） were higher under drought stress at different concentrations of PEG-6000.The seed germination of the two materials was better than that of other breeds. The germination rate, germination potential, germination index, and vitality index of No.3（A. adsurgens Pall.cv.chunjiang No.1） were lower than other materials. The order of the drought resistance of 6 Astragalus was: No.1（Astragalus purdomii）, No.6（Astragalus herb）, No.5（Astragalus laxmannii）, No.4(Astragalus adsurgens Pall., No.2（A. adsurgens Pall.cv.zhongsha No.1）, No.3（A. adsurgens Pall.cv.chunjiang No.1）. The results showed that the drought resistance of 6 different plants of Astragalus had great differences. The effects of certain concentration of PEG-6000 drought stress on seed germination of different materials were different, among which No.1 had the strongest drought resistance and No.3 had the weakest drought resistance.