Microplastic Phytotoxicity in Plants: Uptake Mechanisms and a PICO-Based Evidence Framework for Mitigation Strategies

CT Microplastics have emerged as persistent contaminants of increasing concern in terrestrial ecosystems, particularly in agricultural soils where plastic residues accumulate through mulching films, compost amendments, sewage sludge, irrigation water, and atmospheric deposition. Recent studies indicate that plants can interact with microplastics through both below-ground and above-ground pathways, leading to adhesion to root and leaf surfaces, partial internalization of nanoscale particles, and limited translocation to aerial tissues under certain conditions. Once associated with plant systems, microplastics can impair root and shoot growth, disturb nutrient uptake, induce oxidative stress, alter soil physicochemical properties, and disrupt rhizosphere microbial communities. At the molecular level, microplastic exposure can influence gene expression related to antioxidant defense, energy metabolism, cell-cycle regulation, and photosynthesis, ultimately affecting plant productivity. In addition to these direct phytotoxic effects, microplastics indirectly affect plants by modifying soil structure, enzymatic activities, microbial dynamics, and nutrient cycling within the rhizosphere. Recent research has identified potential mitigation strategies, including biochar amendments, beneficial microbial inoculation, silicon and selenium supplementation, and antioxidant or hormonal priming.