Nickel (Ni) is recognized as most toxic heavy metal that prevails in the environment through anthropogenic activities. The remediation of Ni polluted soil is necessary. Phytoextraction is gaining attention globally due to cost effectiveness, acceptability by the community and high removal efficiency. Numerous organic acids have previously reported to achieve maximum efficiency of phytoextraction. Current study was planned to evaluate the potential of Alternanthera bettzickiana in Ni contaminated soils in alone and with combination of citric acid (C.A). Different physiological, morphological and biochemical characteristics of A. bettzickiana were observed during the pot scale experiment. Plant cuttings of A. bettzickiana were grown in pots filled with 5kg/pot. Nickel Nitrate [Ni(NO₃)₂] was used as a source of Ni. Different levels of Ni and citric acid were applied (Ni0, Ni5mM, Ni10mM, C.A 2.5mM, Ni5+C.A2.5mM, Ni10+C.A2.5mM) in alone and with combination in soil culture. Results from photosynthetic pigments, antioxidants indicate that the application of C.A reduced metal toxicity and enhanced plant defensive mechanism against Ni stress. Furthermore, Catalase (CAT) and superoxide dismutase (SOD) activities were increased in plants with increasing metal concentration in the media. Ni content in different plants was in the order of leaves>stem>roots. Thus, we can conclude that A. bettzickiana seems to be valuable for the phytoextraction of Ni contaminated soils.

Key Words: A. bettzickiana, Antioxidants, Citric Acid, Nickel, Phytoextraction, Soil pollution