Accumulation of microplastics in tomato (Solanum lycopersicum L.)

In recent years, it has been proven that microplastics penetrate seeds, roots, stems, leaves, fruits and plant cells, and the ability for translocation and bioaccumulation depends mainly on their size and type. The aim of this study is to track the bioaccumulation of microplastics in tomato (Solanum lycopersicum L.), which was chosen due of its global economic importance and widespread cultivation. Furthermore, commonly used mulching and drip irrigation practices are a significant source of microplastics in agricultural soils - a prerequisite of crop contamination. The biotesting was carried out under controlled conditions, using 0.1 L vessels, filled with standardized soil substrate, and three fractions (1 μm, 5 μm, 100 μm) of fluorescent polystyrene microplastics (0.01% v/w). After a period of 40 days, the penetration and accumulation of microplastics in all underground and aboveground organs of tomato – roots, stem, leaves – was proven. The amount of microplastics was higher in the underground biomass (root system) compared to the aboveground biomass (stem and leaves) in all experimental variants. Microplastics accumulated in plants have an impact on their growth and biomass synthesis, which is most pronounced in the finest of the studied fractions - 1 μm (p<0.05). Microplastics also have a suppressive effect on the biosynthesis of photosynthetic pigments, and hence - on the intensity of the photosynthesis process, again most pronounced in the fraction of 1 μm (p<0.05). It has been confirmed that the size of plastic particles is an important factor determining their ability to bioaccumulate and the degree of impact on the vital processes of plants. Future research should focus on the precise pathways through which microplastics are absorbed by plant roots and translocated to aerial tissues, as well as uncovering how plants respond at the transcriptomic, proteomic, and metabolomic levels when exposed to microplastics. Long-term field trials under real agricultural conditions are essential to overcome the limitations of laboratory experiments and to assess effects on crop yield, food safety, soil health, and agroecosystems over time.