Effects of Microplastics and its Combination with Cadmium on Pinus Massoniana  Are Dependent on the Type of Microplastics

Abstract

The widespread occurrence of microplastics (MPs) in various environments globally often coincides with the presence of toxic heavy metals, leading to co-contamination toxicity in plants. However, the differences between conventional and degradable MPs and their effects on tree responses to heavy metals remain inadequately understood. Here, we conducted a pot experiment to investigate the effects of different types of MPs (i.e., polyethylene (PE) and polylactic acid (PLA)), in combination with cadmium (Cd), on the growth, physiological and biochemical traits of Pinus massoniana seedlings. The results shows that 10% PE-only was more harmful to the growth and physiology of P. massoniana compared to 10% PLA-only. Furthermore, 1% MPs and 1% MPs + Cd did not significantly impact growth. Nevertheless, under 10% PLA, the growth was significantly higher than that of 10% PLA + Cd. Under treatments of MPs + Cd, 10% PLA enhanced Cd absorption by the roots, while other treatments inhibited Cd uptake. Overall, the effects of MPs and its combination with cadmium on P. massoniana were dependent on the type of MPs, providing significant implications for tree seedling cultivation and forest management in the context of increasing human activities.

Keywords: Microplastics, cadmium, physiology, combined stress, trees