Translocation of nanoplastics from soil to crops impairs pollen viability with potential implications to pollinators

Abstract

Soils are nowadays considered among the major storage sites and sources of nanoplastics (size <1000 nm) entering the natural environment through sewage sludge, abandoned wastes, agricultural activities, and atmospheric deposition. Due to their peculiar chemical and physical properties, nanoplastics can easily interact with plants including crops and potentially translocate up to leaves and flowers entering the food chain, with potential toxic effects to the plants as well as exposing pollinators. In the present study, we assess (1) the uptake, translocation, and effects of polystyrene nanoparticles (PSNPs, approx. 20 nm) in pumpkin (Cucurbita pepo L.) as a model crop plant and (2) PSNP translocation in flowers and effects on pollen. To investigate the uptake and translocation of PSNPs, we used ¹⁴C-radiolabeled PSNPs ([¹⁴C]PSNPs) at concentrations similar to those expected in the environment (1 μg L⁻¹) and under worst-case pollution scenarios (1 mg L⁻¹). The effects of PSNPs on the crops have been observed from both labeled and unlabeled particles. The effects have been observed during germination up to plant development and flower production in pumpkin (C. pepo L.). For the first time, our study provides evidence of [¹⁴C]PSNP uptake by plant roots and translocation from roots to flowers, with subsequent effects on pollen. Most notably, PSNP effects were observed on the apical region of secondary roots, which reveals a significant increase in ROS production, and in primary leaves with significant reduction in the efficiency of photosystems. [¹⁴C]PSNPs were detected in pumpkin flowers and mostly in the anthers whose pollen showed a significant reduction in viability associated with abnormalities in morphology and hydration. Our study provides compelling evidence that nanoplastics are capable of translocating from soil up to the flowers and affecting pollen, raising significant food safety concerns and potential ecological implications on pollinators.