为了探明不同根瘤菌菌株对Cu和Cd污染土壤中苜蓿（Medicago sativa Linn.）的影响，对Cu和Cd污染土壤中（质量分数分别为20和2 mg·kg^-1）接种根瘤菌菌株SM14-3、SM3-2、SM1和SM13-2后苜蓿的生长指标、主要营养元素含量和相应重金属含量进行了比较，并对这些指标进行了Pearson相关性分析。结果表明：Cu和Cd污染土壤中，未接种根瘤菌但施氮（阳性对照）的苜蓿地上和地下部Cu和Cd含量均显著（P<0.05）低于未接种根瘤菌且不施氮（阴性对照），生长指标及地上和地下部N和P含量多显著高于阴性对照，而地上和地下部K含量多低于阴性对照。Cu污染土壤中，接种SM14-3、SM3-2和SM1的苜蓿地上和地下部Cu含量均显著低于阴性对照，接种4个根瘤菌菌株的苜蓿株高、根长、单株地上和地下部干质量、地上和地下部N和P含量以及地下部K含量多显著高于阴性对照。Cd污染土壤中，接种SM14-3的苜蓿地上和地下部Cd含量以及接种SM3-2和SM1的苜蓿地上部Cd含量均显著低于阴性对照；接种4个根瘤菌菌株的苜蓿单株地上和地下部干质量多显著高于阴性对照；接种SM14-3的苜蓿地上和地下部N、P、K含量均显著低于阴性对照，而接种SM3-2、SM1和SM13-2的苜蓿地上和地下部N、P、K含量变化各异。比较来看，Cu和Cd污染土壤中，接种SM14-3和SM3-2的苜蓿各指标总体上表现较好。相关性分析结果表明：地上部指标中，Cu含量与N含量、P含量和株高分别呈极显著（P<0.01）负相关、显著正相关和显著负相关，Cd含量与株高呈显著负相关；地下部指标中，Cd含量与单株地下部干质量和根长呈极显著负相关。研究结果显示：供试根瘤菌菌株对Cu和Cd污染土壤中苜蓿的生长总体上有促进作用，并在一定程度上阻隔苜蓿对土壤中Cu和Cd的吸收，其中，SM14-3和SM3-2的作用突出，可作为Cu和Cd污染土壤中苜蓿高效、安全生产的备选菌株。

  In order to investigate the effects of different rhizobial strains on Medicago sativa Linn. in Cu- and Cd-contaminated soil, the growth indexes, major nutrient element contents, and corresponding heavy metal contents of M. sativa inoculated with rhizobial strains SM14-3, SM3-2, SM1, and SM13-2 in Cu- and Cd-contaminated soil (mass fractions of  20 and 2 mg·kg^-1 respectively) were compared, and the Pearson correlation analysis was conducted for these indexes. The results show that in Cu- and Cd-contaminated soil, the Cu and Cd contents in above- and under-ground parts of M. sativa uninoculated with rhizobia but applied with nitrogen (positive control) are both significantly (P<0.05) lower than those of M. sativa uninoculated with rhizobia and not applied with nitrogen (negative control), the growth indexes and the N and P contents in above- and under-ground parts are mostly significantly higher than those of the negative control, while the K contents in above- and under-ground parts are mostly lower than those of the negative control. In Cu-contaminated soil, the Cu contents in above- and under-ground parts of M. sativa inoculated with SM14-3, SM3-2, and SM1 are all significantly lower than those of the negative control, and the plant height, root length, dry masses of above- and under-ground parts per plant, N and P contents in above- and under-ground parts, and K content in under-ground part of M. sativa inoculated with four rhizobial strains are mostly significantly higher than those of the negative control. In Cd-contaminated soil, the Cd contents in above- and under-ground parts of M. sativa inoculated with SM14-3, as well as the Cd content in aboveground part of M. sativa inoculated with SM3-2 and SM1, are all significantly lower than those of the negative control; the dry masses of above- and under-ground parts per plant of M. sativa inoculated with four rhizobial strains are mostly significantly higher than those of the negative control; the N, P, and K contents in above- and under-ground parts of M. sativa inoculated with SM14-3 are significantly lower than those of the negative control, while the N, P, and K contents in above- and under-ground parts of M. sativa inoculated with SM3-2, SM1, and SM13-2 show different variations. In comparison, in Cu- and Cd-contaminated soil, the indexes of M. sativa inoculated with SM14-3 and SM3-2 are generally better. The correlation analysis result shows that among indexes of above-ground part, Cu content shows an extremely significant (P<0.01) negative correlation, a significant positive correlation, and a significant negative correlation with N content, P content, and plant height respectively, Cd content shows a significant negative correlation with plant height; among indexes of under-ground part, Cd content shows extremely significant negative correlations with dry mass of under-ground part per plant and root length. It is suggested that the test rhizobial strains have promoting effects on the growth of M. sativa in Cu- and Cd-contaminated soil in general, and hinder the absorption of Cu and Cd in soil by M. sativa to a degree, in which, SM14-3 and SM3-2 exhibit the prominent effects, and they can be used as candidate strains for efficient and safe production of M. sativa in Cu- and Cd-contaminated soil.