Environmental levels of microplastics disrupt growth and stress pathways in edible crops via species-specific mechanisms

Zhangling Chen^1,2*Laura J Carter²Steven A Banwart¹Paul Kay²

• ¹School of Earth and Environment, University of Leeds, Leeds, United Kingdom
• ²School of Geography, University of Leeds, Leeds, United Kingdom

Microplastics (MPs) are emerging contaminants in agricultural soils. However, the responses of different plant species to MP stress under soil conditions across varying concentration levels, as well as the underlying mechanisms, remain insufficiently understood. This study examined the morphological, physiological, and biochemical responses of Chinese cabbage (Brassica rapa) and cherry radish (Raphanus sativus) grown in soil containing polystyrene microplastics (PS-MPs) at concentrations of 10, 50, and 100 mg/kg. PS-MPs significantly changed key soil properties, soil pH increased and water-holding capacity improved, these changes promoted early seed germination in both species. In later growth stages, MPs accumulated on cherry radish roots and caused a 35.0% reduction in root length and a 20.4% decrease in fruit diameter. These effects were linked to physical blockage and oxidative stress. In Chinese cabbage, MPs reduced petiole number by 41.7% and leaf area by 35.9% at 10 and 50 mg/kg. These changes were mainly caused by soil structure disruption and nutrient loss. The most severe stress responses were observed at low (10 mg/kg) and medium (50 mg/kg) concentrations, suggesting a non-linear dose–response pattern. Regression analysis revealed distinct ecotoxicological mechanisms in the two species. In cherry radish, MPs adhered to root surfaces and caused mechanical blockage and local oxygen deficiency, consistent with physical toxicity. In contrast, Chinese cabbage showed little root surface accumulation but responded with changes in antioxidant systems and redox balance. This indicates that oxidative stress was the dominant mechanism in this species. These findings support current toxicological models and highlight the importance of plant–particle interactions in shaping crop responses. The results provide new insight into MP phytotoxicity and inform future risk assessments under realistic soil conditions.