Root wounds facilitate the uptake of microplastics in crop plants.

Abstract

Microplastics can be absorbed by plant roots and enter the food chain. Throughout the plant life cycle, roots frequently encounter various physical injuries. However, whether these prevalent injuries serve as critical pathways for microplastics entry into plants remains unknown. Here, we demonstrate that both shallowly wounded roots (injuries limited to the cortex) and unwounded roots exhibit effective resistance to the penetration of microplastics. In contrast, deep wounds (injuries extending to the stele) in roots provide a rapid pathway for microplastics to enter crops such as taro (Colocasia esculenta) and maize (Zea mays). Microplastics are rapidly transported upward via wound-exposed xylem vessels in both vermiculite and soil culture conditions. When 20% of the roots were subjected to deep wounds and exposed to vermiculite containing 50 mg kg^-1 of polystyrene microplastics, the accumulation levels in taro corms reached 161.1 ± 26.4 (1 μm) and 135.6 ± 24.9 (5 μm) items g^-1, while in maize stems reached 503.4 ± 147.4 (1 μm) and 222.3 ± 63.8 (5 μm) items g^-1. Our findings provide substantial evidence that root wounds facilitate the uptake, translocation, and accumulation of microplastics in crops, underscoring the urgent need for proper farming practices to prevent root injuries and enhance food safety.