Species-Specific Foliar Absorption and Translocation of Nanoplastics in Leafy Vegetables Revealed through Isotopic, Physiological, and Transcriptomic Analyses

Understanding the foliar absorption and translocation of atmospherically deposited nanoplastics (NPs) in crops is critical for food safety, yet species-specific mechanisms remain inadequately understood, hindering accurate risk assessment for edible crops. In this study, the isotopic tracing (²H-labeled polystyrene NPs) was employed to systematically compare NPs uptake in three leafy vegetables: cherry radish, water spinach, and lettuce. Stable isotope analysis revealed species dependent accumulation under foliar spraying of NPs, with the highest levels observed in leaves of cherry radish (5.1 to 216.3 μg/g dw), followed by water spinach and lettuce. NPs were translocated to roots of cherry radish and lettuce but restricted to stems of water spinach. Scanning electron microscopy visualized NPs in stomatal cavities and roots of cherry radish and lettuce, as well as in the nodes of water spinach. Mechanistic studies linked these differences to three factors: leaf structure and vascular architecture affected NP absorption and transport; plant physiological traits regulated NP content in leaves; and transcriptomic data indicated that gene expression related to the abscisic acid-ROS-Ca²⁺ mediates stomatal closure pathway. Our findings elucidate how NPs are absorbed and translocated across plant species and highlight species-specific responses to atmospheric NP pollution and associated risks.