Plant–Microbe Interaction in Heavy-Metal-Contaminated Soils

Heavy metals are the most important inorganic pollutants, which are not degraded and progressively accumulate in the environment. The use of plants for rehabilitation of heavy-metal-contaminated soils is an emerging area of interest, because it provides an ecologically and environmentally sound and safe method for restoration and remediation. Although a number of plant species are capable of hyperaccumulation of heavy metals, however, this approach is not applicable for remediating sites with multiple contaminants. The biogeochemical capacities of microorganisms seem almost limitless and they can adsorb and accumulate metals in their cells and are being used in microbial leaching and also as agents of cleaning the environment. To overcome the metal stress, numbers of mechanisms have been evolved by microorganisms of agronomic importance by which they tolerate and promote the uptake of heavy metal ions. Such mechanisms include: the pumping of metal ions exterior to the cell, accumulation and sequestration of the metal ions inside the cell, transformation of toxic metal to less toxic forms, and adsorption/desorption of metals. The best approach would be to combine the advantages of plant–microbe interactions within the plant rhizosphere into an effective cleanup technology. The activities of plants and plant/microbial associations may offer viable means of accomplishing the in situ remediation of contaminated soils. This chapter examines the potential role of plant–microbe interactions in heavy-metal-contaminated soils toward phyto-bioremediation.