Plastic nanoparticles can be absorbed by plants in a similar manner to inert metal or metal oxide particles, suggesting that defense mechanisms that could protect them evolved in plants long before the emergence of human-made plastic pollution, according to Adolphe Merkle Institute researchers. 

In a News & Views article published in the leading science journal Nature Nanotechnology, Dr. Fabienne Schwab and the AMI’s BioNanomaterials co-chairs Profs. Alke Fink and Barbara Rothen-Rutishauser have commented on a recent and widely discussed study from Sun and co-workers stating that plants can absorb plastic nanoparticles, or nanoplastics. The study, published in June in the same journal, investigated how plastic nanoparticles could infiltrate a plant’s vascular system, and what effect they could have on its growth. By combining different microscopy methods, and labeling plastic nanoparticles with metals or fluorescent dyes, the researchers based in China and the United States were able to demonstrate that negatively-charged particles were able to make their way into the root vasculature of Arabidopsis (thale cress), a widely used plant model. High concentrations of the particles, up to 185 times those of microplastics detected for example in floodplain soils, also reduced plant growth, although less so in soil rather than in a culture medium. According to Sun and co-workers, their investigations provided “direct evidence that nanoplastics can accumulate in plants, depending on their surface charge,” adding that that accumulation may have “direct ecological effects and implications for agricultural sustainability and food safety.”

Schwab and her co-authors have welcomed this first insight into interactions between terrestrial plants and plastic nanoparticles, notably in showing how to overcome the challenge of detecting polymers within the complex plant biopolymer matrix. They pointed out that the relatively moderate biochemical defense responses to the nanoplastic particles were very much alike the responses of plants to metal and metalloid (oxide) nanoparticle exposure. Most likely, the majority of the particles did not enter the plant, but only interacted with its surfaces. They added that these modest responses despite the use of high concentrations of plastic nanoparticles indicates that plants already benefit from robust physiological barriers and biochemical defense mechanisms because of much earlier interactions with natural nanoparticles in their environment.    

Reference: Schwab, F.; Rothen-Rutishauser, B.; Petri-Fink, A. When Plants and Plastic Interact. Nature Nanotechnology 2020, 15 (9), 729–730.