摘要： 为探明外源油菜素内酯（Brassinosteroids，BRs）调控紫花苜蓿苗期耐盐性的生理机制，选用陇中苜蓿和中苜3号紫花苜蓿幼苗为试验材料，采用营养液水培法，在150 mmol/L NaCl胁迫下，叶片喷施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胁迫下紫花苜蓿幼苗株高、地上生物量、渗透调节能力和抗氧化能力的影响。结果表明：150 mmol/L NaCl胁迫下，陇中苜蓿和中苜3号紫花苜蓿幼苗的株高和地上生物量显著下降（P<0.05），叶片中的可溶性蛋白含量和CAT活性均显著降低（P<0.05），活性氧（O₂^-·、OH^·、H₂O₂）大量积累（P<0.05），膜脂过氧化产物MDA含量显著增加（P<0.05）。150 mmol/L NaCl胁迫下，喷施0.1 μmol/L外源EBR后，陇中苜蓿幼苗的株高和中苜3号幼苗的地上生物量显著增加（P<0.05），陇中苜蓿和中苜3号紫花苜蓿幼苗叶片中的可溶性蛋白含量显著提高（P<0.05），酶促抗氧化系统（SOD、GPX、APX、GR、CAT）活性和非酶抗氧化系统（GSH、AsA）活性均显著提高（P<0.05），活性氧（O₂^-·、OH^·、H₂O₂）产生量显著下降（P<0.05），膜脂过氧化程度显著降低（P<0.05）。说明NaCl胁迫下，喷施外源EBR能够增强紫花苜蓿幼苗的渗透调节能力，提高苜蓿幼苗酶促抗氧化系统和非酶促抗氧化系统活性，抑制苜蓿幼苗体内活性氧的大量积累，进而降低NaCl胁迫对苜蓿幼苗造成的渗透胁迫和氧化损伤程度，明显促进苜蓿幼苗的生长，对于提高紫花苜蓿苗期耐盐性具有积极的作用。

关键词: 紫花苜蓿, 2,4-表油菜素内酯, NaCl胁迫, 渗透调节, 抗氧化系统

Abstract: To explore the physiological mechanism of exogenous brassinosteroids (BRs) regulating salt tolerance of alfalfa seedling, the seedlings of M. sativa cv. Zhongmu No.3 and M. sativa cv. Longzhong were selected as the experimental materials, water culture with nutrient solution was used, under 150 mmol/L NaCl stress, the leaves were sprayed with 0.1 μmol/L exogenous 2,4-epibrassinolide (EBR), the effects of exogenous EBR on plant height, aboveground biomass, osmoregulation and antioxidant capacity of alfalfa seedlings under NaCl stress were studied. The results showed that:under 150 mmol/L NaCl stress, the seedling height and aboveground biomass of Zhongmu No.3 and Longzhong decreased significantly, the content of soluble protein and CAT activity in leaves decreased significantly, active oxygen (O₂^-·, OH^·, H₂O₂) accumulated in large quantities, MDA content of membrane lipid peroxidation products increased significantly. Under 150 mmol/L NaCl stress, after spraying 0.1 μmol/L exogenous EBR, the seedling plant height of Longzhong and the seedling aboveground biomass of Zhongmu No.3 increased significantly,the content of soluble protein in the leaves of Longzhong alfalfa and Zhongmu No.3 alfalfa seedlings increased significantly, the content of soluble protein in leaves increased significantly, the activities of SOD, GPX, APX, GR, CAT and GSH, AsA increased significantly, the production of active oxygen (O₂^-·, OH^·, H₂O₂) decreased significantly, and the degree of membrane lipid peroxidation decreased significantly. The results showed that under NaCl stress, the application of exogenous EBR could enhance the osmotic regulation ability of alfalfa seedlings, increased the activities of enzymatic antioxidant system and non enzymatic antioxidant system of alfalfa seedlings, and inhibit the accumulation of active oxygen in alfalfa seedlings. All above resulted in the reduction of osmotic stress and oxidative damage caused by NaCl stress on alfalfa seedlings, and the significant promotion of alfalfa seedlings growth, which having a positive effect on improving salt resistance of alfalfa seedling.

Key words: Medicago sativa, 2,4-epibrassinolide, NaCl stress, Osmotic adjustment, Antioxidant system

中图分类号: 

• S634.3