Uptake and effect of carboxyl-modified polystyrene microplastics on cotton plants

Microplastics (MPs) have emerged as a significant global environmental concern, particularly within agricultural soil systems. The extensive use of plastic film mulching in cotton cultivation has led to the alarming presence of MP pollution in cotton fields. However, the uptake and effects of MPs on the growth of cotton plants are poorly understood. In this study, we conducted a comprehensive analysis of hydroponically cultured cotton seedlings at the phenotypic, transcriptional, and metabolic levels after exposure to carboxyl-modified polystyrene microplastics (PS-COOH). Treatment with three concentrations of PS-COOH (100, 300, and 500 mg/L) resulted in notable growth inhibition of treated plants and exhibited a dose-dependent effect. And, PS-COOH can invade cotton roots and be absorbed through the intercellular spaces via apoplastic uptake, with accumulation commensurate with treatment duration. Transcriptomic analysis showed significant up-regulation of genes associated with antioxidant activity in response to 300 mg/L PS-COOH treatment, suggesting the induction of oxidative stress. In addition, the PS-COOH treatment activated the phenylpropanoid biosynthesis pathway, leading to lignin and flavonoid accumulation, and altered sucrose catabolism. These findings illustrate the absorption and effects of MPs on cotton seedlings and offer valuable insights into the potential toxicity of MPs to plants in soil mulched with plastic film. Microplastics are of global environmental concern, particularly in agricultural systems. Cotton is a typical crop that is grown utilizing plastic mulching techniques, which is a common practice to improve crop yield. This study comprehensively evaluated the physiological effects and genetic changes in hydroponically cultured cotton seedlings at the phenotypic, transcriptional, and metabolic levels under different PS-COOH particle concentrations. The results provide insights into the internal speared of MPs within plants, and present a theoretical basis for further investigation into the adverse effects of MPs on crops in field environments. The RNA-seq data in the study has been submitted to NCBI Gene Expression Omnibus (GEO) with accession number GSE240032. Other data supporting the findings of the study are available within the paper and within its supplementary materials.