Phosphate-solubilizing bacteria improve the phytoremediation efficiency of Wedelia trilobata for Cu-contaminated soil

In a controlled experiment, we assessed the effect of phosphate-solubilizing bacterium (PSB) on the soil metal (Cu²⁺) phytoremediation by Wedelia trilobata and examined the effect of the interaction of Cu contamination and PSB on the growth of W. trilobata. We also explored the effect of the interaction of Cu contamination and PSB on the soil microflora. The results showed that the removal efficiency of Cu from soil by W. trilobata increased with an increase in the concentration of PSB, and the translocation factors of Cu (i.e., leaf:root and stem:root) were both significantly upregulated by PSB. The PSB significantly promoted the growth of W. trilobata; however, the effect of the Cu-PSB interaction on the leaf net photosynthetic rate (Pn) of W. trilobata was not significant, whereas copper contamination had a significant negative influence on the soil microflora, PSB had a significant positive influence on the soil microflora. Thus, PSB improved the phytoremediation efficiency of W. trilobata in Cu-contaminated soil because of the positive influence on the soil microflora, improving soil quality, which then increased the growth of W. trilobata in Cu-contaminated soil. The vigorous growth of W. trlobata led to higher of Cu absorption and translocation from soil as the ultimate result.