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Applying chemical enhancements may improve the phytoremediation of soils contaminated with heavy metals. This pot experiment study assessed the ability of Amaranthus hybridus L. to bioaccumulate Cd, both alone and with the addition of chelators. Ethylenediamine triacetic acid (EDTA) was added at concentrations of 1.5 and 3.0 mmol·kg-1; and nitrilotriacetic acid (NTA) was added at concentrations of 2.5 and 5.0 mmol·kg-1 to assess the plant's ability to uptake Cd when the soil was contaminated at concentrations of 5 to 40 mg kg-1 Cd. Adding EDTA and NTA enhanced the accumulation capacity of Cd in the plant shoots. Cd concentrations in the plant shoots were higher with the EDTA treatment than with the NTA treatment. This indicates that EDTA treatments enhanced Cd phytoremediation in this species more than NTA. Applying 1.5 and 3.0 mmol·kg-1 EDTA for the soil contaminated with 40 mg kg-1 Cd resulted in up to 100 mg·kg-1 Cd in the plant shoots, exceeding the critical content (100 mg·kg-1) for Cd-hyperaccumulators. The total Cd uptake in plants was higher in EDTA treatment than in NTA treatment, suggesting that EDTA more effectively enhanced Cd accumulation in A. hybridus. The most Cd accumulation in shoots, 1181.57μg·pot-1, was seen when 1.5 mmol·kg-1 EDTA was used with soils contaminated with 40 mg Cd kg-1. In conclusion, A. hybridus may be an attractive candidate for phytoremediation through Cd-hyperaccumulation, with the application of EDTA. [ABSTRACT FROM AUTHOR]

Heavy metal (HM) toxicity is one of the major abiotic stresses leading to hazardous effects in plants; many of them are toxic even at very low concentration. Pollution of the biosphere with heavy metal has accelerated dramatically since the industrial revolution. A common consequence of HM toxicity is the excessive accumulation of Reactive Oxygen Species (ROS), which can cause peroxidation of lipids, oxidation of protein, inactivation of enzymes, DNA damage and/or interact with other vital constituents of the plant cells. Plants respond to avoid detrimental effects of HM in a variety of different ways such as restriction of uptake and transport of metals, plasma membrane exclusion, chelation and sequestration of heavy metals by ligands such as phytochelatins and metallothioneins, induction of heat shock proteins, biosynthesis of polyamines, and production of antioxidants (Enzymatic and non enzymatic). This review focuses on sources of HM and its toxicity with special reference to Cadmium, tolerance mechanism in plants and molecular approaches to overcome its deleterious effects on plants. [ABSTRACT FROM AUTHOR]