Arbuscular mycorrhiza alters maize zinc uptake differentially from nano- vs. bulk-ZnO particles

The increasing application of nanotechnology and beneficial microbiomes in agriculture highlights the need to understand the role of arbuscular mycorrhiza fungi (AMF) in the uptake and distribution of nanoparticles (NPs) in host plants. In this study, we investigated the effects of different ZnO particle sizes (NPs and bulk) and concentrations (0, 200, 400, and 800 mg/kg) on zinc uptake by maize ( Zea mays ) grown with or without AM-fungus Funneliformis mossae . Our results showed that neither ZnO particle form nor AMF presence significantly affected maize shoot biomass. However, 200 mg/kg ZnO concentration in both bulk and NPs, enhanced root biomass, indicating a concentration-dependent effect of Zn on plant growth. 800 mg/kg ZnO, regardless of particle size, reduced AMF colonization by 16.6 % (bulk) and 22.1 % (NPs) compared to the control, demonstrating a negative impact of elevated Zn on the plant-AMF symbiosis. Interestingly, despite reduced colonization, AMF external hyphal length increased in the 400 and 800 mg/kg ZnO NP treatments, suggesting that the utilization of AMF hyphae represents a potential strategy to reduce Zn toxicity. Analysis of Zn concentrations revealed that, in the absence of AMF, shoot Zn concentrations were 28 % higher in plants treated with bulk ZnO as compared to ZnO NPs, whereas this difference between ZnO forms disappeared in the presence of AMF. Moreover, AMF inoculation decreased Zn concentrations in roots for both bulk and NPs treatments, while in shoots, AMF reduced Zn concentration by 52 % in the bulk treatment across all concentrations, highlighting the protective role of AMF against heavy metal toxicity. These findings demonstrate that Zn uptake and distribution in maize depend on ZnO particle size and are strongly influenced by AMF. The observed changes in external hyphal length further suggest that this parameter should be considered in future studies on plant–AMF–NPs interactions. • Elevated Zn concentrations from both particle forms reduced AM fungal colonization. • Increased ZnO NPs concentrations increased fungal hyphal length. • ZnO NPs treatments resulted in lower shoot Zn concentrations compared to bulk ZnO. • AMF reduced Zn concentrations in roots (for both NPs and bulk ZnO) and in shoots (bulk ZnO). • Zn distribution patterns in maize differed between ZnO particle sizes.