Phytoremediation Potential of Heavy Metal(loid)-Contaminated Soils Using Indigenous Mycorrhizal Fungi and Soil Microbiota to Enhance Plant Metal Uptake: A Field Study and Greenhouse Experiments

This study aims to figure out the key factors influencing fungal infection rates in trees growing in urban soils and to further evaluate the best combination of fungal and soil microbial inoculation for enhancing plant tolerance to soil contamination under greenhouse conditions through plant-fungi symbiosis. Overall, field evaluations showed that mercury (Hg) (0.59-1.91 mg/kg) exceeded the Dutch target values at all sites. Besides, principal component analysis (PCA) and Pearson correlation analysis revealed that environmental variables, particularly total S (r=-0.211, p<0.05) and K (r=-0.258, p<0.05), were negatively correlated with fungal infection rates. The second part of this study conducted greenhouse experiments to examine the potential of using mycorrhizal fungi taken from the field to support plant growth (i.e., Arabidopsis thaliana and Cynodon dactylon) for phytoremediation purposes. The results demonstrated that inoculation with Funneliformis mosseae (M) on A. thaliana and C. dactylon, either alone or in combination with indigenous soil microbiota (B+M) greatly promoted the growth of both test plant species in the pot experiment, as evidenced by the significantly increased (p<0.05) mycorrhizal infection rates, biomass, photosynthetic pigment contents and phosphorus concentrations compare with the control. In particular, when comparing all treatments in both test plant species, most measured plant growth and physiological parameters were significantly higher (p<0.05) in the B+M treatment than in the M treatment, indicating that certain plant species, when co-inoculated with suitable mycorrhizal fungi and indigenous beneficial soil microbiota, may exhibit enhanced effective adaptation to heavy metal(loid)-polluted soil conditions compared with inoculation with mycorrhizal fungal alone.