盐胁迫下紫花苜蓿种子萌发对外源2,4-表油菜素内酯诱导的生理响应

Physiological responses of Medicago sativa seedgermination induced by exogenous 2,4-epibrassinolide under salt stress

摘要:

外源油菜素内酯(Brassinosteroids,BRs)能够促进盐胁迫下紫花苜蓿(Medicago sativa)种子的萌发,本研究以陇中苜蓿和中苜3号紫花苜蓿种子为材料,在150 mmol/L NaCl胁迫下,添加0.1 μmol/L 外源2,4-表油菜素内酯(2,4-epibrassinolide,EBR),研究外源EBR对NaCl胁迫下紫花苜蓿种子萌发及生理的影响,旨在明确外源BRs诱导盐胁迫下紫花苜蓿种子萌发的生理机制。结果表明:(1)150 mmol/L NaCl胁迫下,两个紫花苜蓿品种的种子萌发、幼苗生长明显受到抑制,种子萌发过程中,蛋白水解酶活性显著提高,可溶性蛋白和可溶性糖含量显著降低,超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GPX)、抗坏血酸过氧化物酶(APX)和过氧化氢酶(CAT)活性显著下降,超氧阴离子自由基(O₂·^-)、羟自由基(OH·)、双氧水(H₂O₂)和丙二醛(MDA)积累量显著增加。(2)150 mmol/L NaCl胁迫下,添加0.1 μmol/L 外源EBR对两个紫花苜蓿品种种子的发芽率、发芽势具有明显的促进作用,并显著提高了种子的发芽指数、活力指数及幼苗的苗高、根长、根系活力和幼苗干重。种子萌发过程中,蛋白水解酶活性显著下降,可溶性糖、可溶性蛋白、游离氨基酸含量显著增加,SOD、GPX、APX、CAT活性显著提高,O₂·^-、OH·、H₂O₂和MDA含量显著降低。说明外源EBR能够有效缓解NaCl胁迫对紫花苜蓿种子萌发和幼苗生长所产生的抑制作用,通过提高渗透调节物质含量和抗氧化酶活性,来维持紫花苜蓿种子萌发过程中的正常的生理生化代谢,降低渗透胁迫和氧化胁迫造成的伤害程度,提高紫花苜蓿种子萌发期的耐盐性。关键词:紫花苜蓿;NaCl胁迫;2,4-表油菜素内酯;种子萌发

Abstract:

The effect of exogenous 2,4-epibrassinolide (EBR,0.1 μmol/L) on seed germination and physiological responses of alfalfa (Medicago sativa cv.Longzhong and Zhongmu No.3) under NaCl stress (150 mmol/L) were studied in order to clarify the physiological mechanism of alfalfa seed germination induced by exogenous BRs under salt stress.The results showed that 1) Under NaCl stress,the seed germination and seedling growth of two varieties were significantly inhibited,during seed germination,the activity of proteolytic enzyme increased significantly,and the content of soluble protein and soluble sugar decreased significantly,the activities of superoxide dismutase (SOD),glutathione peroxidase (GPX),ascorbic acid peroxidase (APX) and catalase (CAT) decreased significantly,and the accumulation of superoxide anion radicals (O₂·^-),hydroxyl radicals (OH·),hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) increased significantly.2) Under NaCl stress,the addition of exogenous EBR significantly promoted the seed germination rate and germination potential of two varieties,and significantly increased the germination index,activity index,seedling height,root length,root activity and seedling dry weight of the seeds.During the germination process,the activity of proteolytic enzyme decreased significantly,soluble sugar and soluble sugar decreased significantly.The activities of SOD,GPX,APX and CAT were significantly increased,while the contents of O₂·^-、OH·、H₂O₂ and MDA were significantly decreased.The results indicated that exogenous EBR could effectively alleviate the inhibition of NaCl stress on seed germination and seedling growth of alfalfa,maintain the normal physiological and biochemical metabolism process of alfalfa seed germination,reduce the damage caused by osmotic stress and oxidative stress,and improve the salt tolerance of alfalfa in seed germination period.