Plants uptake chemicals and other smaller molecules through their roots. Oftentimes they will store pollutants in their fruit or stems because they don’t know what to do with it.
Here’s an article from Nature that specifically studied plastic uptake by plant roots.[1]
Yes, at the um scale and below it does happen, and such concentrating effects can really change it from a non-issue to a serious problem, depending on how chemically active the contaminant is.
TFA: "Yet despite all the new knowledge about microplastics and the even tinier nanoplastics, smaller than a millimeter, that enter the human body through ingestion or inhalation"
Microplastics are apparently taken as being a mm or larger, and 'nanoplastics' are anything smaller than a mm which is still very large. The ones you are talking about would be very much smaller than those by another 3 orders of decimal magnitude.
The article specifically says micrometer so it would be right between millimeter and nano sized plastics. They will only get smaller as they degrade.
> Our results provide evidence in support of submicrometre- and micrometre-sized polystyrene and polymethylmethacrylate particles penetrating the stele of both species using the crack-entry mode at sites of lateral root emergence.
