In vitro bioaccumulation potential and biochemical, enzymatic and non-enzymatic antioxidant responses of Acacia modesta Wall. callus to cadmium, nickel and lead

Callus was initiated from the internode of Acacia modesta Wall. It was used as a model plant system for screening heavy metal tolerance. Sterilized internodes were cultured under aseptic conditions. Two concentrations, (10 and 15 mg/L), of 2,4-dichlorophenoxyacetic acid (2,4-D) were supplied to the media. Cadmium (Cd), nickel (Ni) and lead (Pb) were used at different concentrations [control (0.0), 0.125, 0.25, 0.5, and 1 ppm]. Bioaccumulation factor (BAF), total carbohydrates, total protein, enzymatic antioxidants, peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), non-enzymatic antioxidants (total phenolics, total flavonoids, saponins, and tannins), and the antioxidant activity were evaluated.Successful callus development was observed in all treatments except in Pb (1ppm). Values of BAFs for the three heavy metals were > 1; arranged in the following order: Pb> Ni> Cd indicating that the callus of A. modesta could be considered as a hyperaccumulator for the three heavy metals. Callus exhibited tolerance to elevated Ni concentrations by stimulating the activity of CAT, POD and SOD as well as enhancing the contents of total flavonoid, saponins and tannins. Increase in CAT activity induced Cd tolerance. Total antioxidant activity increased with increasing Cd and Ni concentrations. Maximum tolerance of A. modesta callus for Pb was indicated at 0.5 ppm. Increase in Pb concentration enhanced SOD activity.Acacia modesta callus demonstrated significant heavy metal tolerance and bioremediation potential for Cd, Ni, and Pb. In vitro cell culture proved to be an effective tool for studying biochemical responses to heavy metals without interfering with the surrounding environment