Nano and submicron fluorescent polystyrene particles internalization and translocation in seedlings of Cichorium endivia L.

Abstract

Contamination by plastics is one of the major causes of pollution of the terrestrial environment. Fragmentation of plastics into micro and nano particles may result in negative interactions between polymers and terrestrial ecosystems. The effects of nano (20 nm) and submicron (200 nm) fluorescent polystyrene (PS) particles, at different concentrations (0.01, 0.1, 1 g L⁻¹), were analysed on chicory plant (Cichorium endivia L.), considering the following endpoints: germination percentage and seedling development after 7 and 14 days exposure; genotoxic effects; polyphenols and photosynthetic pigments content, antioxidant activity; absorption and translocation of PS particles in the seedling tissues. The results indicated no negative effects on germination of both PS particles' sizes at any concentration; seedlings elongation was affected by 1 g L⁻¹ of 20 nm PS after 7 days exposure. Cytological analysis revealed no mitotic activity inhibition, but an uprising of chromosomal abnormalities in all treatments. Interestingly, photosynthetic pigments always increased after PS exposure. Seedlings treated with 20 nm PS showed intense fluorescence in the roots of 7 days and in the shoots of 14 days, while 200 nm PS treated seedlings exhibited low fluorescence. Electron microscopy and infrared spectroscopy confirmed 20 nm PS internalization and transport inside the plant tissue and a reduced presence of 200 nm PS. These results suggest the importance not only of particle size in plastic internalization in plant tissues, but also of cytological damages induced by particles too large to be bioaccumulated. From both aspects, consequences may arise for plant fitness, food safety and human health.