Monitoring the stress resistance of Pennisetum purpureum in Pb (II) contaminated soil bioaugmented with Enterobacter cloacae as defence strategy

Lead (Pb) is reported to have negative effects on the biogeochemical behaviour of the plant growth. In recent years, the significance of rhizoremediation of heavy metals has been of great focus aiding in the development rates of plants under stressed conditions. The present study evaluated the physio-biochemical response of Pennisetum purpureum to different concentrations of Pb (II) viz., 0, 50, 100 and 150 mg kg−1 in the form of lead (II) nitrate. The pre-characterized PGPR strain, Enterobacter cloacae - KU598849 was used to augment the plants. After Pb exposure for 45 d, parameters such as plant growth, lead accumulation, H2O2 content, MDA content, protein, proline content and antioxidant enzymatic activities were quantified. Results illustrated that increasing Pb concentration reduced the early growth, metal accumulation, protein content and affected physio-biochemical changes by causing oxidative damage in plants. Upon augmentation of the bacterial inoculum, the plants significantly resisted the toxic effects of Pb. Increased Pb bioaccumulation pattern was recorded in roots than shoots, were highest uptake was found to be 72 mg kg−1 dry weight when exposed to 150 mg kg−1 Pb concentration. Lead supplementation increased the activities of malonylaldehyde (MDA), superoxide dismutase (SOD), peroxidase (POX), ascorbate peroxidase (APX) and catalase (CAT) in P. purpureum. Bacterial bioaugmentation resulted in the reduction of the oxidative stress aided with reduced antioxidant enzyme activities indicating the minimization of the damages under stress.