Plastic particles adsorb to the roots of freshwater vascular plant Spirodela polyrhiza but do not impair growth

Here we investigated the impact of nano- and microplastics on the freshwater duckweed species Spirodela polyrhiza, a vascular plant. S. polyrhiza was exposed for 120h to concentrations ranging from 102 to 106 particles·mL-1. We assessed impacts on growth and chlorophyll production, and explored adsorption and absorption by way of confocal microscopy. For both nano- and micronized particles no concentration-dependent impacts on growth were found (expressed as fresh weight, frond and root sizes). In addition, chlorophyll contents were not significantly impacted. Confocal microscopy indicated that nano-sized plastic particles adsorbed externally to the duckweed, especially to the roots. Internalized plastic particles could not be detected. Nevertheless, given their important role in ecosystems as a food source for a range of organisms, the adsorption of plastic particles to S. polyrhiza roots as detected in this study can result in the transfer of plastic particles to diverse herbivorous species within the ecosystem.