Autotoxicity of maize and its mitigation by plant growth promoting rhizobacterium Paenibacillus polymyxa

We studied the autotoxic effects of maize (Zea mays) on some biophysical and biochemical parameters. In addition, we observed the role of plant growth promoting rhizobacterium Paenibacillus polymyxa in mitigating the adverse effects of autotoxicity. The seedlings inoculated with P. polymyxa and without extract produced maximum dry weight, root and shoot length. Autotoxicity decreased the dry weight, root and shoot length of maize seedlings. A significant decrease in total chlorophyll, protein content and nitrate reductase activity was found in the maize seedlings treated with residue extract without bacterial inoculation. However, chlorophyll and protein contents increased in inoculated seedlings treated with lower concentration of extract. The inoculation also increased the nitrate reductase activity in inoculated maize seedlings than non inoculated control and also influenced the activities of various antioxidant enzymes. Extract at higher concentration decreased the activities of antioxidant enzymes, viz. superoxide dismutase, catalase and peroxidase. Inoculation of seedlings with the bacterium significantly altered the activities of antioxidants and decreased the electrolyte leakage and lipid peroxidation. These results suggested the protective nature of P. polymyxa against autotoxicity of maize.