Charge-selective polystyrene nanoplastic retention by plant cell walls: Pectin domains dictate differential accumulation in rice seedling roots and shoots

The escalating global plastic pollution necessitates urgent investigation into the distribution and accumulation pathways of nanoplastics (NPs) in crops to assess their threats to food security. Here, we reveal that plant cell walls serve as a charge-selective barrier governing the differential uptake of polystyrene (PS) NPs with distinct surface charges (PS-COOH NPs and PS-NH₂ NPs) in rice. Quantitative tracking showed that PS-COOH NPs accumulated 1.84- and 4.43-fold more in roots and shoots, respectively, than PS-NH₂, with >92% of both NPs restricted to roots. Crucially, root cell walls selectively retained NPs based on charge: PS-NH₂ NPs accumulated 1.91-2.45-fold more than PS-COOH NPs within walls, primarily through binding to pectin (74.04%-87.28% sequestration). Furthermore, NPs induced cell wall remodeling, including pectin enrichment, hemicellulose I deposition, thereby reinforcing charge-selective retention and differential uptake. These findings reveal an adaptive mechanism of plant cell walls under NPs stress and provide mechanistic insights into charge-dependent NPs accumulation pathways in edible crops.