Size- and charge-dependent phytotoxicity of polystyrene nanoplastics to Vallisneria natans.

Smaller, positively charged 30 nm PS-NPs cause the most severe phytotoxicity to Vallisneria natans, reducing biomass by 29.5% and impairing Photosystem II function.

• Why it matters: Understanding size- and charge-dependent effects of nanoplastics on aquatic plants is crucial for assessing ecological risks in contaminated freshwater ecosystems.
• What they did: The study exposed Vallisneria natans to 30 nm and 300 nm PS-NPs with -NH2 and -COOH groups over 30 days, measuring growth, photosynthesis, microstructure, oxidative stress, and microbial community changes.
• The result: Findings show smaller, positively charged PS-NPs induce greater physiological damage, oxidative stress, and microbial community shifts, highlighting their environmental threat to submerged macrophytes.