Effects of three different microplastics on wheat growth and nitrogen utilization

Abstract As a new type of pollutant, microplastics exist widely in agricultural soil and may pose a threat to crop growth and food safety. As an important crop, wheat plays an important role in the development of agricultural economy. The effects of three different types of microplastics, polyethylene (PE), polyvinyl chloride (PVC) and polyethylene terephthalate (PET) on the growth and nitrogen uptake and utilization of wheat were investigated. The results showed that PE treatment significantly increased the total biomass of wheat by 16% compared to the control group on day 30, while PVC and PET treatment also showed a positive effect on day 72, with a total biomass increase of 16% and 12%, respectively. In terms of nitrogen absorption, PET treatment significantly increased the total nitrogen content of wheat leaves and roots, and the 15N utilization rate of wheat leaves increased by 28% on day 58, and the 15N utilization rate of wheat roots increased by 16% on day 72. PE and PVC treatments significantly increased the total nitrogen content of wheat root by 24% and 18%, respectively, on day 72. PE, PVC and PET treated wheat stem total nitrogen content decreased significantly. In addition, the addition of microplastics also had an impact on the abundance of soil nitrogen conversion functional genes, some microplastics treatment promoted the abundance of soil denitrification genes, while the impact on the abundance of ammonia oxidation genes was small. On the 72nd day, PVC treatment increased the soil nirK gene abundance by 240%, and PET treatment increased by 231%. These results indicated that microplastics could promote wheat growth and nitrogen utilization to some extent, and provided scientific basis for understanding the role of microplastics in agro-ecosystem.