Phytoremediation potential of ornamental plants for heavy metal removal from contaminated soil: a critical review

Soil contamination by heavy metals has become a serious environmental issue considering its effects on health and the environment. Several techniques are being used for the treatment of contaminated soil, but these methods have limitations on account of cost, chemical/energy efficiency, and application in the field. On the other hand, phytoremediation is a cost-effective, solar energy-driven, and eco-friendly method for heavy metal removal. The present study discusses hyperaccumulating ornamental plants that can remove metal contaminants from the soil without any visible phytotoxic symptoms. Besides the uptake and translocation, the specific metal accumulation potential of ornamental plants, the mechanism involved in the removal, and the growth response of hyperaccumulators towards metal exposure have also been discussed. The essential indices- bioconcentration factor and translocation factor to determine the suitability of plants towards phytoextraction, the role of different plant parts in translocation and biochemical mechanisms for detoxification of metals have been presented as a highlight of this study. For optimum removal and efficient management of a phytoremediation design, the role of controlling factors such as soil characteristics, type of metal, plant species, organic amendments, phytochelators, bio-inoculants, etc. is very important. Considering the advent of biotechnology, the use of genetically modified plants is also recommended for significantly improved efficiency. It is expected that the present study will provide a guiding path for future researchers in exploring the scope of phytoremediation using ornamental plants.