Two studies on sub-micrometre plastic particles provide evidence of plastic accumulation in terrestrial plants.
Plastic waste is attracting growing research attention, especially in the environmental science community. It is also a topic that can trigger the interest of the general public because of its high visual impact. Most research efforts so far have focused on monitoring the fate of plastic microparticles, and to a certain extent nanoparticles, in water, and their interaction with aquatic organisms, in the attempt to estimate how much plastic such organisms uptake and ultimately how toxic the plastic can be.
Comparatively, less attention has been given to the uptake of plastic particles by terrestrial plants. This is however becoming quite relevant for the potential negative effect that plastic can have on the environment generally, and more specifically on agriculture. The Letter by Xiao-Dong Sun and co-workers now published in Nature Nanotechnology, and the Article by Lianzhen Li and co-workers now published in Nature Sustainability are significant advances in our knowledge because they report experimental evidence of plastic particle uptake by a number of terrestrial plants.
The work by Sun et al. focuses on how the charge of plastic nanoparticles around 200 nm in size affects the uptake by the standard model species Arabidopsis thaliana. Artificially synthesized plastic nanoparticles were added to the soil. Positively charged particles were then seen accumulating in the roots and even affecting root growth, while negative particles were observed also in the plant vasculature
Li et al. focused on particles ranging from 200 nm to a few micrometres and they studied the uptake in wheat and lettuce. Through high-resolution scanning electron microscopy, it was possible to establish that plastic particles of different sizes enter the plants by the so-called crack-entry mechanism, through openings in the roots that are also known to be entry points for bacteria in plants developing infections.
The ultimate goal of research on plastic particles is to understand how toxic they can be for organisms in the environment and, to be fair, neither result answers that question yet. But knowing the details of how much and through which mechanism the particles accumulate in plants is a crucial first step and provides an important starting point for studies of toxicity.