以“拉丁诺”（Ladino）白三叶为供试材料，研究NaCl对PEG（聚乙二醇6000）水分胁迫下白三叶幼苗叶片相对含水量、根系活力、叶绿素含量、活性氧成分、膜相对透性和膜脂过氧化、抗氧化防御及有机渗透调节物质积累的影响。外源NaCl能显著提高水分胁迫下叶片相对含水量和根系活力，有效降低叶绿素的分解；通过增强水分胁迫下叶片SOD、POD和CAT活性及抗坏血酸-谷胱甘肽循环（AsA-GSH cycle）关键酶活性，维持了细胞内显著较低的活性氧、电解质渗透率和MDA含量，缓解了胁迫对细胞造成的氧化性伤害；50 mmol／L NaCl对正常水分条件下白三叶的生长也具有一定的促进作用；但外源NaCl预处理使水分胁迫下白三叶叶片内可溶性糖和游离脯氨酸含量显著降低。说明NaCl显著提高白三叶的抗旱性与增强胁迫下白三叶抗氧化防御系统密切相关，并非促进了植物体内有机渗透调节物质的积累，而可能像其他旱生植物一样是通过富集Na＋提高其渗透调节能力来发挥作用。%Effects of NaCl on relative water content,root viability,chlorophyll content,reactive oxygen spe-cies,relative membrane permeability and membrane lipid peroxidation,antioxidant defence and accumulation of osmoregulatory substances in white clover (Trifoliumrepens)under water stress induced by PEG-6000 were analyzed.Under water stress,exogenous NaCl significantly improved relative water content and root viability, and effectively reduced the decomposition of chlorophyll in leaves.The treatment of exogenous NaCl improved SOD,POD,CAT activities and the key enzymes of AsA-GSH cycle activities and maintained significantly low-er electrolyte leakage and MDA content,thereby reducing water deficit stress injury to plants.50 mmol/L NaCl also can improve the growth of white clover under normal water availability,but the accumulation of sol-uble sugar and free proline was significantly lower in the exogenous NaCl treatment under water deficit stress. The results suggested that exogenous NaCl can effectively improve water deficit stress tolerance of white clover with mechanisms including enhanced antioxidant defence,but not accumulation of more osmoregulatory sub-stances.The reason maybe that white clover is like other xerophytes which accumulate Na+ as an osmoregula-tory solute under drought stress.
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