Transgenerational Transfer and Effects of Polystyrene Nanoplastics in the Floating Macrophyte Spirodela polyrhiza

Nanoplastics (NPs) represent an emerging threat to aquatic ecosystems. However, their transgenerational transfer potential and associated toxicological consequences remain poorly characterized. In this study, the transgenerational transfer of polystyrene (PS) NPs was quantified and visualized in the floating macrophyte Spirodela polyrhiza using the metal-doped and bioimaging method. Beyond parental (F0) S. polyrhiza uptake via frond lower epidermis, PS accumulated through stipule-mediated mother-to-daughter frond transfer (MF-to-DF transfer) with an efficiency of 1-3%. Both F0 uptake and MF-to-DF transfer were insensitive to environmentally relevant PS weathering. The F1-to-F2 transfer efficiency exhibited a clear dose-dependent increase, rising from 0.2 to 0.6% at 0.1 mg L^-1 to 0.7-1.1% at 5 mg L^-1. Notably, a pronounced F2-specific phytotoxicity emerged, which was closely correlated with reduced growth (9 ± 4% lower specific growth rate) and frond number (12 ± 7% decline), whereas no comparable inhibition was observed in F1. Mechanistically, this phytotoxicity stemmed from transcriptional reprogramming (dysregulated circadian/photosynthesis-antenna pathways, activated stress resistance metabolites) at 5 mg L^-1. These findings established that parental NP exposure could induce transgenerational growth inhibition in unexposed offspring; however, the extent to which these mechanistic observations apply to environmental scenarios (e.g., 0.1 mg L^-1) remains to be determined. This represented a significant yet under-characterized ecotoxicological risk, and it critically escalated NP impacts from individual-level toxicity to population-relevant consequences in aquatic ecosystems.