Occurrence and distribution of micro/nanoplastics in soils and their phytotoxic effects: A review

Some recent studies have reviewed the occurrence and phytotoxicity of micro/nanoplastics, but their distribution in the soil environment, mechanisms of uptake by roots and the mode of action are unclear. Thus, this review comprehensively represents the relative abundance of micro/nanoplastics in different soil types and their toxicities in plants with insights into their partitioning to different soil matrices, uptake mechanisms, and the mode of action. Partitioning of micro/nanoplastics to different soil matrices (like-soil particles, naturally occurring soil organic matters, pore waters and soil fauna) could modify their bioavailability to plants. The small micro/nanoplastic particles can be taken up by roots through the apoplastic and symplastic pathways. In this regard, cellular endocytosis and aquaporin might play a significant role. The shape of the polymers can also regulate their uptake, and the polymers with spherical shapes are more easily absorbed by roots than the polymers with other shapes. Bioaccumulation of micro/nanoplastic induces oxidative stress, which, in turn, causes alterations of gene expressions and different metabolic pathways responsible for plant growth, biomass production and synthesis of secondary metabolites.