Effects of different microplastics on the activation of soil potassium by ectomycorrhizal fungi

    In this study, ectomycorrhizal fungus Lactarius deliciosus (Ld) was used as the test strain, with polypropylene (PP) and polylactic acid (PLA) used as test materials, to investigate the influence of microplastics (MPs) on the capacity of ectomycorrhizal fungi to activate soil insoluble potassium (K). The results showed that both types of MPs could negatively affect the growth of Ld, and PLA exerted a stronger inhibitory effect. Meanwhile, as the MPs concentration increased, the soil available K content decreased initially and then increased. Compared with that in the control group, the soil available K content in the 100 mg/L PP and PLA treatments decreased by 27.57% and 27.33%, respectively. In contrast, the soil available K content was less affectde under high concentrations of MPs. This may be attributed to the stimulation of Ld by high concentrations of of MPs to secrete large amounts of organic acids and hydrogen ions to alleviate environmental stress, thereby promoting the activation of soil K to some extent. In addition, the K content in soil mineral fractions decreased, while the soil slow-release K content increased. However, these variation trend s were attenuated with the addition of MPs. These findings not only reveal the effect of MPs pollution on  the activation of soil K by ectomycorrhizal fungi, but also provide an important theoretical basis for the developing ecological control strategies.