Maize adaptation to low-dose nanoplastic–lead co-contamination: Foliar metabolic reprogramming and phyllospheric microbiome restructuring

Nanoplastics (NPs) and lead (Pb), as emerging environmental pollutants, have been rarely studied in terms of their combined effects on crop growth and metabolic processes under low-dose co-exposure conditions. This study simulated rain-mediated co-exposure of maize seedlings to NPs and Pb at environmentally relevant concentrations (400 μg/L) to elucidate the metabolic responses in leaves and the dynamics of phyllosphere microbial communities. Short-term exposure (45 days) to NPs and Pb did not significantly impair maize seedling growth; however, it induced the accumulation of essential macronutrients in leaves. The metabolic adaptation of maize leaves to NPs and Pb exposure was characterized by a reduction in carbon metabolic flux coupled with an enhancement in lipid metabolic flux. Furthermore, plants responded to co-exposure by activating key metabolic pathways such as those involving ABC transporters, nucleotide metabolism, and amino acid metabolism. Concurrently, the phyllosphere microbiome exhibited structural reorganization, with enrichment of stress-tolerant microbial taxa (e.g., Acidobacteria, Chloroflexi), activation of microbial redox systems, and enhanced capacity of the leaf microbiota to adapt to NPs and Pb exposure. The findings offer theoretical insights into assessing agricultural environmental impacts associated with combined exposure to emerging pollutants, phyllosphere microbial ecology, and plant stress resistance.