2,4-表油菜素内酯对PEG胁迫下紫花苜蓿种子萌发和抗氧化系统的影响OA

Seeds of two alfalfa cultivars,'Zhongcao No.3'and'Juneng',were pretreated with 0,0.01,0.10,or 1.00 µmol/L 2,4-epibrassinolide(EBR)and then germinated under PEG-induced drought stress at an osmotic potential of-0.6 MPa.Germination rate,root length,activities of catalase(CAT),superoxide dismutase(SOD),peroxidase(POD),and ascorbate peroxidase(APX),and malondialdehyde(MDA)content were measured to evaluate the effects of exogenous EBR pretreatment on alfalfa seed germination under drought stress.The results showed that PEG stress significantly inhibited germination of'Zhongcao No.3'but had a weaker inhibitory effect on'Juneng'.Exogenous 0.01 µmol/L EBR promoted recovery of the germination rate of'Zhongcao No.3'under stress,whereas 0.01,0.10,and 1.00 µmol/L EBR reduced the germination rate of'Juneng'under PEG stress.At the optimal EBR concentration,SOD,POD,CAT,and APX activities increased significantly in both cultivars,while MDA content decreased markedly(P<0.05),indicating that EBR alleviated oxidative damage by enhancing antioxidant enzymes activities.Overall,exogenous EBR can effectively alleviate drought stress during alfalfa germi-nation,but its final effect depends on cultivar and concentration.Cultivar-specific seed-soaking protocols should therefore be developed for practical application.