Nanoscale zero-valent iron (nZVI) might generate positive and negative effects on plant growth, since it acts as either hazardous or growth-promotion role. It is still unclear whether such dual roles can be mediated by arbuscular mycorrhizal fungi (AMF) in plant-AMF symbiosis. We first identified that in 1.5 g kg⁻¹ nZVI (≤1.5 g kg⁻¹ positively), maize biomass was increased by 15.83%; yet in 2.0 g kg⁻¹ nZVI, it turned to be declined by 6.83%, relative to non-nZVI condition (CK, p < 0.05), showing a negative effect. Interestingly, the inoculation of AMF massively improved biomass by 45.18% in 1.5 g kg⁻¹ nZVI, and relieved the growth inhibition by 2.0 g kg⁻¹ nZVI. The event of water use efficiency followed similar trend as that of biomass. We found that proper concentration of nZVI can positively interact with rhizosphere AMF carrier, enabling more plant photosynthetic carbon to be remobilized to mycorrhiza. The scanning of transmission electron microscopy showed that excessive nZVI can infiltrate into root cortical cells and disrupt cellular homeostasis mechanism, significantly increasing iron content in roots by 76.01% (p < 0.05). Simultaneously, the images of scanning electron microscopy showed that nZVI were attached on root surface to form an insoluble iron ion (Fe³⁺) layer, hindering water absorption. However, they were efficiently immobilized and in situ intercepted by extraradical hyphae in mycorrhizal-nZVI symbiosis, lowering iron translocation efficiency by 6.07% (p < 0.05). Herein, the optimized structure remarkably diminished aperture blockage at root surface and improved root activities by 30.06% (p < 0.05). Particularly, next-generation sequencing demonstrated that appropriate amount of nZVI promoted the colonization and development of Funneliformis mosseae as dominant species in rhizosphere, confirming the positive interaction between AMF and nZVI, and its regulatory mechanism. Therefore, dual effects of nZVI can be actively mediated by AMF via rhizosphere interactions. The findings provided new insights into the safe and efficient application of nanomaterials in agriculture.

纳米级零价铁 (nZVI) 可能对植物生长产生积极和消极的影响，因为它既可以起到危险的作用，也可以起到促进生长的作用。目前尚不清楚植物-AMF 共生中的丛枝菌根真菌 (AMF) 是否可以介导这种双重作用。我们首先发现，在 1.5 g kg ^-1 nZVI（≤1.5 g kg ^-1阳性）中，玉米生物量增加了 15.83%；然而，在 2.0 g kg ^-1 nZVI 中，相对于非 nZVI 条件（CK，p  < 0.05），它下降了 6.83%，显示出负面影响。^{有趣的是，AMF 的接种在 1.5 g kg -1} nZVI中显着提高了 45.18% 的生物量，并减轻了 2.0 g kg ^-1的生长抑制nZVI。水分利用效率的事件与生物质的事件具有相似的趋势。我们发现，适当浓度的 nZVI 可以与根际 AMF 载体发生正向相互作用，使更多的植物光合碳重新活化到菌根中。透射电镜扫描显示，过量的nZVI可渗入根皮层细胞，破坏细胞稳态机制，使根中铁含量显着增加76.01%（p  < 0.05）。同时，扫描电镜图像显示，nZVI附着在根表面形成不溶性铁离子（Fe ³⁺) 层，阻碍吸水。然而，它们在菌根-nZVI共生中被根外菌丝有效固定和原位截获，使铁转运效率降低了6.07%（p  < 0.05）。其中，优化后的结构显着减少了根面的孔隙堵塞，使根系活性提高了 30.06% ( p  < 0.05)。特别是二代测序表明，适量的nZVI促进了苔藓漏斗形藻的定殖和发育。作为根际优势种，证实了 AMF 和 nZVI 之间的正向相互作用及其调控机制。因此，AMF 可以通过根际相互作用主动介导 nZVI 的双重作用。这些发现为纳米材料在农业中的安全有效应用提供了新的见解。