Potential translocation process and effects of polystyrene microplastics on strawberry seedlings

A growing body of concerns focuses on microplastics as an emerging threat to terrestrial soil-plant ecosystems, but few previous studies have concentrated on asexual plants. To fill this knowledge gap, we carried out a biodistribution study of polystyrene microplastics (PS-MPs) of different particle sizes in strawberry (Fragaria × ananassa Duch. cv. "Akihime") seedlings via the hydroponic cultivation method. Confocal laser scanning microscopy (CLSM) results indicated that both 100 and 200 nm PS-MPs entered the roots and were further translocated to the vascular bundle through the apoplastic pathway. Both PS-MP sizes were detected in the vascular bundles of the petioles after 7 d of exposure, indicating a xylem-based upward translocation pathway. After 14 d, continuous upward translocation of 100 nm PS-MPs was observed above the petiole, while 200 nm PS-MPs could not be directly observed in the strawberry seedlings. This means that the uptake and translocation of PS-MPs depended on the size of PS-MPs and appropriate timing. The significant influence of strawberry seedling's antioxidant, osmoregulation, and photosynthetic systems（p < 0.05）was presented at 200 nm PS-MPs than 100 nm PS-MPs. Our findings provide scientific evidence and valuable data for the risk assessment of PS-MP exposure in asexual plant systems such as strawberry seedlings.