Divergent Responses of Rice ( Oryza sativa L.) Cell Wall to Cd Phytotoxicity Affected by Continuous Nanoplastics Stimulation

The co-occurrence of nanoplastics (NPs) and heavy metals in agricultural environments presents emerging risks to crop safety, yet the dosage-dependent effects of NPs on their joint phytotoxicity, especially at the cell wall (CW) level, remain poorly understood. In this study, we examine how NPs influence cadmium (Cd) phytotoxicity in rice ( Oryza sativa L.), with a particular focus on the root CW. Our results reveal a dosage-dependent “double-edged sword” effect: low-dosage NPs immobilized 72.3% of Cd in the root, while high-dosage NPs disrupted CW integrity, facilitating 34.4% Cd translocation to shoots and exacerbating phytotoxicity. Low-dosage NPs exposure activated carbohydrate and lignin metabolic pathways, increasing the CW thickness by 46.7% and limiting Cd entry. Conversely, high-dosage exposure triggered oxidative stress, impairing CW biosynthesis, causing structural collapse, and increasing CW permeability, thus enhancing Cd uptake. This research improves our understanding of NPs-heavy metal interactions and provides insights for agricultural risk assessment amidst rising plastic pollution.