Accumulation of heavy metals in soil is of concern to the agricultural production sector, because of the potential threat to food quality and quantity. Inoculation with plant growth-promoting bacteria (PGPR) has previously been shown to alleviate heavy metal stress but the mechanisms are unclear. Potential mechanisms by which inoculation with Bradyrhizobium japonicum CB1809 affected the legume soybean ( Glycine max cv. Zeus) and the non-legume sunflower ( Helianthus annus cv. Hyoleic 41) were investigated in solution culture under 5 μM As stress. Adding As resulted in As tissue concentrations of up to 5 mg kg −1 (shoots) and 250 mg kg −1 (roots) in both species but did not reduce shoot or root biomass. Inoculation increased root biomass but only in the legume (soybean) and only with As. Inoculation resulted in large (up to 100%) increases in siderophore concentration but relatively small changes (±10–15%) in auxin concentration in the rhizosphere. However, the increase in siderophore concentration in the rhizosphere did not result in the expected increases in tissue N or Fe, especially in soybean, suggesting that their function was different. In conclusion, siderophores and auxins may be some of the mechanisms by which both soybean and sunflower maintained plant growth in As-contaminated media.

中文翻译：

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评估日本慢根瘤菌CB1809的植物生长促进和砷耐受潜力

由于对食品质量和数量的潜在威胁，土壤中重金属的积累是农业生产部门关注的问题。先前已证明接种植物生长促进细菌 (PGPR) 可减轻重金属胁迫，但其机制尚不清楚。在 5 μM As 压力下的溶液培养中研究了接种 Bradyrhizobium japonicum CB1809 影响豆科植物大豆（Glycine max cv. Zeus）和非豆科向日葵（ Helianthus annus cv. Hyoleic 41）的潜在机制。添加 As 导致两种物种中 As 组织浓度高达 5 mg kg -1 （枝条）和 250 mg kg -1 （根），但没有减少枝条或根生物量。接种增加了根生物量，但仅在豆科植物（大豆）中且仅在含砷时增加。接种导致铁载体浓度大幅增加（高达 100%），但根际生长素浓度变化相对较小（±10-15%）。然而，根际铁载体浓度的增加并没有导致组织 N 或 Fe 的预期增加，特别是在大豆中，表明它们的功能不同。总之，铁载体和生长素可能是大豆和向日葵在受砷污染的培养基中维持植物生长的一些机制。