Nanoplastics interfere with plant-mycorrhizal communication and limit plant growth.

More than 80% of land plants form symbiotic relationships with arbuscular mycorrhizal (AM) fungi for nutrient uptake. As emerging soil pollutants, nanoplastics (NPs) accumulate in both crop and AM fungal tissue, posing non-negligible toxicity and health risks. However, whether and how NPs can impact plant-AM fungal partnership throughout the symbiotic process remains poorly understood. Here, using axenic root-fungal culture, fluorescence NP tracking, and real-time symbiotic signal monitoring, we show that during pre-colonization phase, NPs reduced spore germination rates (-48%) due to the NP accumulation on spore surface, hindering symbiotic signal perception. During the colonization phase, NPs entered fungal cells, disrupted organelles, and accelerated hyphal senescence, consequently reducing hyphal branching length (-22%) and secondary spore production (-32%). In real-world soil, inoculation of secondary spores (reproduced under NPs) formed fewer arbuscule structures (-46%) within maize roots with reduced carbon allocation to AM fungus, leading to a lower hyphal length density (HLD) (-24%). During the post-colonization phase, lower HLD impaired the well-known function of phosphorus (P) mineralization by hyphae-enriched bacteria, reduced soil available P (-5.7%) and maize shoot P (-20%), eventually resulting in compromised plant performance. Our findings reveal an integrated yet largely underexplored mechanism of how NPs hinder plant performance by disrupting the dynamic relationship between plants and their symbiotic partners. In a broader context, understanding the alteration of plant-microbial interaction (rather than separately) under emerging stress can provide ecologically relevant implications for sustaining agricultural and terrestrial ecosystems.