Abstract: In order to study the effects of rhizobium on the remediation of cadmium contaminated soil by alfalfa (Medicago sativa L.),alfalfa was inoculated with or without rhizobia under low nitrogen (1 mmol·L^-1) and high nitrogen (4 mmol·L^-1) levels,and the plant height,biomass,cadmium content and nitrogen content in aboveground and belowground parts,chlorophyll and malondialdehyde content in leaves were measured. The results showed that under Cd stresses increasing nitrogen level could significantly increase plant height and biomass,chlorophyll content and Cd content in leaves (P<0.05). Inoculating rhizobia could increase nitrogen content,plant height,biomass,chlorophyll content and Cd content in leaves,and decrease MDA content (P<0.05). In conclusion,rhizobia could alleviate the toxicity of heavy metal Cd by increasing nitrogen content,and promote the absorption of Cd by alfalfa,indicating that rhizobium has great potential and broad application prospects in the remediation of Cd contaminated soil.

Key words: Alfalfa, Cadmium stress, Nodule nitrogen fixation, Bioremediation

摘要： 为研究根瘤菌对紫花苜蓿修复镉污染土壤的作用，本试验在低氮素（1 mmol·L^-1）和高氮素（4 mmol·L^-1）水平下对接种和不接种根瘤菌的紫花苜蓿（Medicago sativa L.）进行镉（CdCl₂）胁迫处理，测定处理后的株高、生物量、地上部和地下部镉含量、氮含量、叶片叶绿素和丙二醛含量。结果表明：在Cd胁迫下，提高氮素水平可显著增加植物株高和生物量、叶片叶绿素含量和Cd含量（P<0.05）；接种根瘤菌可提高紫花苜蓿氮素含量，增加植物的株高、生物量、叶片叶绿素含量和Cd含量，降低丙二醛含量（P<0.05）。综上所述，根瘤通过增加氮素含量缓解重金属Cd的毒害，并促进紫花苜蓿对Cd的吸收，表明根瘤菌在Cd污染土壤的修复中具有较大潜力和广阔的应用前景。

关键词: 紫花苜蓿, 镉胁迫, 根瘤固氮, 生物修复