Uptake and translocation of polystyrene nanoplastics in edible plants via root and foliar exposure: A qualitative imaging-based study

Understanding the uptake and internal distribution of nanoplastics in edible crops is critical to assessing environmental and food safety risks. This study examined the localisation and translocation of fluorescent polystyrene nanoplastics following root and foliar exposure in three major crop species: lettuce, carrot, and wheat. Using confocal and scanning electron microscopy, we detected clear internalisation of nanoplastics in root, stem, and leaf tissues, with significant variation among species and exposure pathways. Following root exposure, nanoplastics were observed in root cortical and vascular tissues across all species. Lettuce exhibited systemic translocation to stems and leaves, while carrot and wheat showed more restricted movement. After foliar exposure, particles were internalised through stomatal and cuticular routes. In lettuce, nanoplastics were also detected in stems and roots, indicating bidirectional transport, whereas downward translocation was minimal or undetectable in carrot and wheat. Surface features such as stomatal density, trichomes, and wax layers influenced particle retention and uptake efficiency. Particles were detected in tissues of all three species, raising potential concerns for human exposure via crop consumption. While imaging confirmed localisation, it remained qualitative; future studies should integrate complementary quantitative techniques and field-relevant conditions. Overall, the findings demonstrate that nanoplastics can be taken up through both foliar and root pathways, with transport efficiency shaped by species-specific anatomical and physiological traits. These results highlight the need for standardised protocols and further research into long-term implications for plant health, trophic transfer, and food safety.