Role of microbial inoculation in phytoremediation of heavy metals by Elsholtzia splendens

A pot culture experiment was conducted to study the role of inoculations with four microbial inocula, singly or in combination, in heavy metal uptake from contaminated soil by Elsholtzia splendens. The four inocula, Glomus caledonium 90036 (36), an inoculum containing mixed arbuscular mycorrhizal fungi (ZJ), an inoculum containing two Cu-tolerant Penicillium species (F) and an inoculum containing mixed Cu-tolerant bacteria (B), were applied to the soil under unsterilized conditions. The control received no inoculation. The plants were harvested after 24 wk of growth. The co-inoculation with 36, ZJ and F was most effective in increasing shoot Cu, Zn, Pb uptake and root Cu, Zn, Cd uptake, indicating that the inoculation combination may be used in phytoextraction of Cu, Zn, Pb and phytostabilization of Cu, Zn, Cd. Most inoculations increased the activities of soil phosphatase and urease, and improved plant growth and P nutrition. Microbial inoculation affected heavy metal uptake and translocation by decreasing soil pH. The results show there may be synergistic effects between arbuscular mycorrhizal fungi and other soil microorganisms on plant growth and heavy metal uptake of E. splendens, and therefore indicate great potential in the phytoremediation of heavy metal-contaminated soil.