Integrated metabolomics and transcriptomics reveal the hormesis-like effects of polyethylene microplastics on Pisum sativum L

Microplastics (MPs) are of great concern because of their potential adverse effects on plant growth. Currently, most studies on the effects of MPs on plant growth have focused on macroscopic aspects, while fewer studies have been conducted at the molecular level. In this study, we combined metabolomics and transcriptomics approaches to reveal the effects of polyethylene microplastics (PE-MPs) on Pisum sativum seedlings and their response mechanisms at the molecular level. The findings indicated that elevated levels of PE-MPs significantly impeded the growth of Pisum sativum seedlings, while lower concentrations of PE-MPs somewhat facilitated the growth of Pisum sativum seedlings. Additionally, laser confocal scanning microscopy clearly demonstrated that PE-MPs can be taken up by the roots, stems, and leaves of Pisum sativum seedlings. Metabolomics and transcriptomics analyses showed that PE-MPs affect growth by influencing tryptophan metabolism and photosynthesis in Pisum sativum seedlings. As the concentration of PE-MPs increased, Pisum sativum seedlings responded to PE-MPs stress by increasing the expression of genes that encode growth hormone synthesis and cell membrane synthesis. This is the first time that the effects of PE-MPs on Pisum sativum seedling growth have been studied at the molecular level, highlighting the potential ecological risks of PE-MPs in agricultural systems.