This paper reviews key aspects of phytoremediation technology and the biological mechanisms underlying phytoremediation. Current knowledge regarding the application of phytoremediation in alleviating heavy metal toxicity is summarized highlighting the relative merits of different options. The results reveal a cutting edge application of emerging strategies and technologies to problems of heavy metals in soil. Progress in phytoremediation is hindered by a lack of understanding of complex interactions in the rhizosphere and plant based interactions which allow metal translocation and accumulation in plants. The evolution of physiological and molecular mechanisms of phytoremediation, together with recently-developed biological and engineering strategies, has helped to improve the performance of both heavy metal phytoextraction and phytostabilization. The results reveal that phytoremediation includes a variety of remediation techniques which include many treatment strategies leading to contaminant degradation, removal (through accumulation or dissipation), or immobilization. For each of these processes, we review what is known for metal pollutants, gaps in knowledge, and the practical implications for phytoremediation strategies.

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The suitability of five plant species was studied for phytoextraction and phytostabilisation in a region with temperate maritime climate of coastal British Columbia, Canada. Pot experiments were conducted using Lolium perenne L (perennial rye grass), Festuca rubra L (creeping red fescue), Helianthus annuus L (sunflower), Poa pratensis L (Kentucky bluegrass) and Brassica napus L (rape) in soils treated with three different metal (Cu, Pb, Mn, and Zn) concentrations. The bio-metric characters of plants in soils with multiple-metal contaminations, their metal accumulation characteristics, translocation properties and metal removal were assessed at different stages of plant growth, 90 and 120 DAS (days after sowing). Lolium was found to be suitable for the phytostabilisation of Cu and Pb, Festuca for Mn and Poa for Zn. Metal removal was higher at 120 than at 90 days after sowing, and metals concentrated more in the underground tissues with less translocation to the aboveground parts. Bioconcentration factors indicate that Festuca had the highest accumulation for Cu, Helianthus for Pb and Zn and Poa for Mn.

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Existing information relating to the application of phytoremediation in arid regions, for mitigating the toxicity of organic and inorganic contaminants is summarized, emphasizing the comparative merits of different phytostrategies. Adverse climatic conditions in arid and semi-arid environments along with the intrinsic abiotic stresses need specific considerations, which are discussed here. The current "state of art" for petrochemical and metal phytoremediation, as well as phytodesalination is presented, making it possible to choose the very best decision, when the technology is applied for various contaminant scenarios. Information is also provided on contaminants in arid regions, remediation approaches and different phytoremediation strategies to be adopted, depending on the nature of contaminants and the site situations. Furthermore, phytodesalination may well occur in parallel with phytoremediation of heavy metal polluted soils in arid regions, enhancing the potential of this process. This has drawn a great deal of interest during recent years and is reviewed here. Finally, the lacunae in the current knowledge are identified, which has to be addressed to improve the effectiveness of phytoremediation under arid conditions.