Toxic effects of larger sized polyethylene microplastics on cucumber root secretion and oxidative stress.

Microplastics (MPs) are widely present in soil and have toxic effects on plants. However, larger particle sizes on the physiological growth characteristics and root exudates of plants remain poorly understood. A hydroponic experiment was conducted with 25 μm polyethylene to explore the toxic effects on the development, root exudates and physiological properties of cucumber. The findings demonstrated that 25 μm PE inhibited plant growth by blocking the lateral roots’ development gap and accumulating on the surface of cucumber root. Both medium and high concentrations of PE adversely affected the root growth of cucumber, and significantly reducing the content of malondialdehyde (MDA) and chlorophyll, decreasing fruit yield, and altering the release of low molecular weight organic acids (LMWOA). Inhibition was most significant at PE concentrations of 80 mg/L. Correlation analysis showed that LMWOA was closely related to plant physiological growth. This study is helpful to elucidate the regulatory mechanism of LMWOA on the accumulation of large-sized MPs in the roots of edible vegetables and offers valuable insights into assessing the potential threats posed by MPs contamination to crops and vegetables.