Silicon regulates microplastic-induced phytotoxicity and its detoxification mechanism: A plant-microbe perspective

Microplastics (MP) threaten agricultural ecosystems by altering soil properties and plant-microbe interactions. This study examined polyethylene microplastics (PE-MP) and silicon (Si) effects on kale growth, soil enzymes, and rhizosphere microbiota. PE-MP reduced kale shoot and root biomass by 11 % and 27 %, respectively, and shifted soil properties (e.g., increased pH, decreased potassium). Si increased biomass by 16 % (shoot) and 25 % (root) versus CK and alleviated PE-MP-induced enzyme inhibition. PE-MP suppressed carbon-cycle enzymes (sucrase, S-β-glucosidase) but enhanced nitrogen-cycle enzymes (urease, N-acetyl-β-D-glucosidase). Si restored sucrase and boosted alkaline phosphatase activity. PE-MP enriched stress-tolerant Proteobacteria and Actinobacteria, while Si promoted beneficial taxa (e.g., Sphingomonas) and mitigated declines in Acidobacteriota and Gemmatimonadota. Co-occurrence networks linked bacterial ASVs to plant physiology, showing Si enhances microbial interactions for nutrient cycling. Si mitigates PE-MP stress via microbial restructuring and enzyme regulation, offering strategies for crop resilience in contaminated soils.