Effect of heavy-metal-resistant bacteria on enhanced metal uptake and translocation of the Cu-tolerant plant, Elsholtzia splendens.

A hydroponics trial was employed to study the effects of Pseudomonas putida CZ1 (CZ1), a heavy-metal-resistant bacterial strain isolated from the rhizosphere of Elsholtzia splendens (E. splendens), on the uptake and translocation of copper (Cu) in E. splendens. Significant promotion of plant growth coupled with the obvious plant-growth-promoting (PGP) characters of the bacteria suggested that CZ1 would be a plant-growth-promoting rhizobacterium (PGPR) to E. splendens under Cu stress condition. The results of inductively coupled plasma optical emission spectrometry (ICP-OES) showed that CZ1 increased the concentration of Cu in the shoots (up to 211.6% compared to non-inoculation treatment) and translocation factor (TF) (from 0.56 to 1.83%) of those exposed to Cu. The distribution of Cu in root cross section measured by synchrotron-based X-ray fluorescence microscopy (SRXRF) indicated that CZ1 promoted the transport of Cu from cortex to xylem in roots, which contributed to the accumulation of Cu in shoots. Furthermore, CZ1 improved the uptake of nutrient elements by plants to oppose to the toxicity of Cu. In summary, P. putida CZ1 acted as a PGPR in resistance to Cu and promoted the accumulation and translocation of Cu from root to shoot by element redistribution in plant root; hence, CZ1 is a promising assistance to phytoremediation.