# Effects of Polypropylene Microplastics and Copper Contamination on Rice Seedling Growth

## TL;DR

This study examines how polypropylene microplastics and copper affect rice seedlings, finding mixed effects on growth and toxicity.

## Contribution

The study reveals that polypropylene microplastics can both enhance copper uptake and partially reduce shoot toxicity in rice seedlings.

## Key findings

- Polypropylene microplastics slightly promoted rice seedling growth while copper inhibited it.
- Co-exposure to polypropylene and copper partially improved shoot growth and reduced peroxidase suppression.
- Root peroxidase activity dropped significantly under combined exposure, indicating root–shoot divergence in antioxidant responses.

## Abstract

This study investigates the effects of polypropylene microplastics (PP-MPs) and copper (Cu), applied individually and in combination, on the growth (root and shoot length, fresh and dry biomass), peroxidase (POD) activity, and Cu accumulation of rice seedlings. A hydroponic experiment was conducted with four treatments: control (CK), PP, Cu, and PP+Cu. Exposure to PP-MPs slightly promoted seedling growth, whereas Cu markedly inhibited growth and induced chlorosis. Compared with Cu alone, co-exposure to PP-MPs and Cu (PP+Cu) partially improved shoot growth and alleviated Cu-induced suppression of shoot POD activity. In contrast, root POD activity showed the strongest reduction under PP+Cu (91.7% decrease), revealing a pronounced root–shoot divergence in antioxidant responses. Moreover, total Cu accumulation in seedlings increased by 12.3% in PP+Cu relative to Cu alone, implying that PP-MPs may influence Cu bioavailability and/or internal partitioning. However, Cu speciation and subcellular distribution were not quantified in this study and should be examined in future work. Overall, PP-MPs may simultaneously enhance Cu uptake while partially mitigating shoot-level toxicity, underscoring the complexity of microplastic–metal co-contamination in rice seedling systems.