Information on phosphorus (P)-solubilizing microorganisms in variable charge soil is lacking. We screened soil microorganisms that can effectively utilize P adsorbed on variable charge minerals using a series of synthetic media of decreased P availability. Rhizospheric soil (Orthic plintaqualt) from a 30-y old tea plant was diluted and aseptically inoculated to a series of media containing P adsorbed on goethite at 0, 255, 50, 75, and 100% saturation. Microorganisms, which survived in the 25% P sorption saturation medium, were each by colony isolates transferred to another freshly prepared medium of the same type for growth stability test. Microbial species, which could grow and reproduce for more than 15 generations in the 25% P-saturation medium were considered as P-solubilizing microbes (PSMs) and used for identification tests. By this procedure, we screened one PSM population which was identified as the bacterium Moraxella sp by Gram staining, Gamma culture and staining, optical and electron microscopic observation, and enzyme-oxidizing reaction. The PSMs have higher maximal transport rates to P than the ubiquitous soil microorganisms and have an optimal temperature of 378C and optimal pH of 5.5-7.5 for growth.

contaminated soils. The results from this study indicate that the plant exhibited high tolerance to Cu toxicity in the soils, and normal growth was attained up to 80mgkg-1 available soil Cu (the NH4OAc extractable Cu) or 1000mg kg-1 total Cu. Under the field conditions, a biomass yield of 9 ton ha-1 was recorded at the soil available Cu level of 77mg kg-1, as estimated by the NH4OAc extraction method. Concentration-dependent uptake of Cu by the plant occurred mainly at the early growth stage, and at the late stage, there is no difference in shoot Cu concentrations grown at different extractable soil Cu levels. The extractability of Cu from the highly polluted soil is much greater by the roots than that by the shoots. The NH4OAc extractable Cu level in the polluted soil was reduced from 78 to 55mgkg-1 in the soil after phytoextraction and removal of Cu by the plant species for one growth season. The depletion of extractable Cu level in the rhizosphere was noted grown in the mined area, even at high Cu levels, the NH4OAc extractable Cu in the rhizosphere was 30% lower than that in the bulk soil. These results indicate that phytoextraction of E. splendens can effectively reduce the plant-available Cu level in the polluted soils.

Phytoremediation is a promising approach for cleaning up soils contaminated with heavy metals. Information is needed to understand growth response and uptake mechanisms of heavy metals by some plant species with exceptional capability in absorbing and superaccumulating metals from soils. Greenhouse study, field trial, and old mined area survey were conducted to evaluate growth response and Cu phytoextraction of Elsholtzia splendens in contaminated soils, which has been recently identified to be tolerant to high Cu concentration and have great potential in remediating