Phosphate-solubilizing bacteria improve the phytoremediation efficiency of <i>Wedelia trilobata</i> for Cu-contaminated soil

In a controlled experiment, we assessed the effect of phosphate-solubilizing bacterium (PSB) on the soil metal (Cu²⁺) phytoremediation by <i>Wedelia trilobata</i> and examined the effect of the interaction of Cu contamination and PSB on the growth of <i>W. trilobata</i>. 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 <i>W. trilobata</i> increased with an increase in the concentration of PSB, and the translocation factors of Cu (<i>i.e.</i>, leaf:root and stem:root) were both significantly upregulated by PSB. The PSB significantly promoted the growth of <i>W. trilobata</i>; however, the effect of the Cu–PSB interaction on the leaf net photosynthetic rate (Pn) of <i>W. trilobata</i> 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 <i>W. trilobata</i> in Cu-contaminated soil because of the positive influence on the soil microflora, improving soil quality, which then increased the growth of <i>W. trilobata</i> in Cu-contaminated soil. The vigorous growth of <i>W. trlobata</i> led to higher of Cu absorption and translocation from soil as the ultimate result.