Unveiling the Impact of Microplastics on Plant Growth and Physiology

Abstract

The widespread prevalence of microplastics (plastic particles smaller than 5 mm) in terrestrial ecosystems has emerged as a pressing global concern. The intensity of this growing challenge is further increasing due to the increased plastic production and less recycling efforts. Plastics that are not recycled often end up in landfills, where they gradually break down into tiny particles through weathering and several physiological and biochemical processes. Over time, these microplastics spread into various environmental compartments, including water bodies, sewage systems, sludge, and agricultural soils. Extensive research has been conducted to investigate the impact of MPs on marine environments. However, their effects on terrestrial ecosystems have largely remained unexplored. Addressing these concerns in polluted agricultural soils is essential for sustaining crop production and food security. In this context, biochar, a carbon-negative technology, has been suggested as a solution to enhance soil quality and improve crop yields, particularly in less fertile soils. However, limited knowledge exists about how biochar interacts with MPs, and whether biochar's presence can modify the impact of MPs on plant growth and physiology. Therefore, our investigation aimed to evaluate the influence of polyvinyl chloride MPs on plant growth and physiology within a soil-plant system. Two experiments were conducted in a controlled glasshouse environment. In the first experiment, we introduced biochar at concentrations of 0% and 0.5% (w/w) into agricultural soil that was contaminated with polyvinyl chloride microplastics (PVC-MPs) at concentrations of 0%, 0.25%, and 0.5% (w/w). Test crop was chosen wheat. In the second experiment, conducted without biochar, we used both industrial and analytical grade PVC microplastics at concentrations of 0%, 0.25%, and 0.5%, individually and in combination. This allowed us to investigate the combined effects of these microplastics on plant growth and physiology. Mash bean was taken as test crop. The results demonstrated that the addition of biochar had a significant positive impact on the photosynthetic and antioxidant activity of wheat plants subjected to PVC-MP stress. In the presence of biochar, plant dry biomass also showed improvement. On the other hand, when a combination of industrial and analytical grade PVC microplastics was introduced, it had a contrasting effect. x This combination significantly reduced the activity of the plant's photosynthetic machinery and triggered an increase in the production of reactive oxygen species (ROS), which was met with an elevation in antioxidant activity