Abstract：
Rhizobium inoculation has been widely applied to alleviate heavy metal (HM) stress in legumes grown in contaminated soils, but it has generated inconsistent results with regard to HM accumulation in plant tissues. Here, we conducted a meta-analysis to assess the performance of Rhizobium inoculation for regulating HM in legumes and reveal the general influencing factors and processes. The meta-analysis showed that Rhizobium inoculation in legumes primarily increased the total HM uptake by stimulating plant biomass growth rather than HM phytoavailability. Inoculation had no significant effect on the average shoot HM concentration (p > 0.05); however, it significantly increased root HM uptake by 61 % and root HM concentration by 7 % (p < 0.05), indicating safe agricultural production while facilitating HM phytostabilisation. Inoculation decreased shoot HM concentrations and increased root HM uptake in Vicia, Medicago and Glycine, whereas it increased shoot HM concentrations in Sulla, Cicer and Vigna. The effects of inoculation on shoot biomass were suppressed by nitrogen fertiliser and native microorganisms, and the effect on shoot HM concentration was enhanced by high soil pH, organic matter content, and phosphorous content. Inoculation-boosted shoot nutrient concentration was positively correlated with increased shoot biomass, whereas the changes in pH and organic matter content were insufficient to significantly affect accumulation outcomes. Nitrogen content changes in the soil were positively correlated with changes in root HM concentration and uptake, whereas nitrogen translocation changes in the tissues were positively correlated with changes in HM translocation. Phosphorus solubilisation could improve HM phytoavailability at the expense of slight biomass promotion. These results suggest that the diverse growth-promoting characteristics of Rhizobia influence the trade-off between biomass-HM phytoavailability and HM translocation, impacting HM accumulation outcomes. Our findings can assist in optimising the utilisation of legume-Rhizobium systems in HM-contaminated soils.
摘要：
根瘤菌接种已广泛应用于缓解污染土壤中豆科植物的重金属（HM）胁迫。但是它在植物组织中的HM积累方面产生了不一致的结果。这里,我们进行了一项荟萃分析，以评估根瘤菌接种在豆科植物中调节HM的性能，并揭示了一般的影响因素和过程。荟萃分析表明，在豆科植物中接种根瘤菌主要通过刺激植物生物量的生长而不是HM植物的利用率来增加HM的总吸收。接种对平均芽HM浓度无显著影响(p>0.05);它显着增加了根HM吸收61％和根HM浓度7％（p<0.05），表明安全的农业生产，同时促进HM植物稳定。接种降低了芽HM浓度，并增加了蚕豆中的根HM吸收，Medicago和甘氨酸,而它增加了苏拉的枝条HM浓度，Cicer和Vigna.氮肥和天然微生物抑制了接种对芽生物量的影响，高土壤pH值增强了对枝条HM浓度的影响，有机质含量,和磷含量。接种促进的芽养分浓度与芽生物量的增加呈正相关，而pH和有机质含量的变化不足以显着影响积累结果。土壤中的氮含量变化与根系HM浓度和吸收的变化呈正相关，而组织中的氮易位变化与HM易位变化呈正相关。磷的溶解可以以轻微的生物量促进为代价来改善HM植物的利用率。这些结果表明，根瘤菌的不同生长促进特性影响生物量-HM植物利用度和HM易位之间的权衡，影响HM积累结果。我们的发现可以帮助优化受HM污染的土壤中豆类-根瘤菌系统的利用。
