Phytoremediation is a potential method for the bioremediation of heavy metal-contaminated soils (Blaylock et al., 1997). Because of the small amount of biomass, slow growth rate and low bioavailability of heavy metal in soils, plant hyper accumulators remove limited amounts of contaminant and are not suitable for use in field phytoremediation(Shen and Liu, 1998; Kayser et al., 2000)