The role of plants and plant/microbial systems in the reduction of exposure.

The activities of plants and plant/microbial associations may offer a viable means of accomplishing the in situ remediation of contaminated soils. Two uses of plants for phytoremediation are reported here. In one set of studies, the ability of plants to foster degradative microorganisms was investigated. Results indicated that the degradation of several chlorinated pesticides increased in rhizosphere soil and that this same increase occurred when unplanted soils were given materials released from plant roots. In current investigations, the potential for plants to remove and accumulate metals from their environment is being considered. This work employs a unique testing system, the target-neighbor method, that allows evaluation of how planting density influences metal uptake. Results of these studies could provide the information needed to manipulate plant density for optimization of metal removal (remediation of metal-contaminated soil) or minimization of the amount of toxic metals in important crops (reduction of human exposure).