A Critical Review of Polystyrene Microplastics in Soil–Plant Systems: Absorption, Phytotoxicity and Future Perspectives

ABSTRACT The extensive utilisation and inadequate disposal of polystyrene microplastics (PS‐MPs) pose significant threats to soil–plant ecosystems. The present review assembles evidence concerning their behaviour and impacts within soil–plant systems. In soils, PS‐MPs alter the composition of microbial communities, elevate respiration stress, and regulate the activity of extracellular enzymes. In term of soil fauna, PS‐MPs show oxidative, genotoxic, and immunological reactions which can slow down decomposition and nutrient cycling. Plants take up PS‐MPs via root and foliar pathways, translocate them through vascular tissues, and accumulate them in metabolically active sites, with consequent inhibition of photosynthesis, hormonal imbalance, and transcriptome and metabolome reprogramming. Interactions with coexisting stressors are context‐dependent: co‐exposure to heavy metals, antibiotics, or phthalates frequently enhances reactive oxygen species formation and nutrient imbalance, whereas adsorption‐driven immobilisation by PS‐MPs can reduce pollutant bioavailability and partially mitigate toxicity. Size dependence is a consistent theme, with nano‐scale fractions showing higher mobility and intracellular access, and micro‐scale fractions exerting stronger physical and adsorptive effects in the rhizosphere. We highlight priorities for field‐realistic, long‐term studies that integrate particle ageing, multi‐stressor experiments, and harmonised exposure metrics, together with nature‐based mitigation strategies. Linking PS‐MPs indicators to soil‐health assessment and land‐degradation frameworks will support risk evaluation and sustainable management of agroecosystems.