Growth response of cowpea (Vigna unguiculata L.) exposed to Pseudomonas fluorescens, Pseudomonas stutzeri, and Pseudomonas gessardii in lead contaminated soil

Lead (Pb) is a major contaminant among heavy metals in the soil environment that has negative impacts on the growth of plants, which ultimately cause health risk via entering into the food chain. In this regard, plant growth promoting rhizobacteria (PGPR) might improve plant growth by counteracting the harmful effects of Pb stress. Therefore, the present pot study was conducted to evaluate the role of PGPR in improving the growth of cowpea in Pb-contaminated soil. Three different concentrations of Pb (250, 350, and 750 mg kg(-1)) were applied alone (control) and in combination with bacterial inoculums [S1 (Pseudomonas fluorescens), S2 (Pseudomonas stutzeri) and S3 (Pseudomonas gessardii)] using completely randomized design each with three replicates. Results showed that plant fresh weight, plant dry weight, shoot length, root length, and chlorophyll contents of cowpea plants were improved significantly (P <= 0.05) by applying bacterial isolates as compared to the un-inoculated contaminated control. Among bacterial isolates, S3 performed better as compared to other bacterial isolates. The maximum increase in plant fresh weight, plant dry weight, shoot length, root length, and chlorophyll content was observed under S3 bacterial strain. Bacterial inoculation also enhanced the Pb concentration in the plant and the maximum uptake was recorded under S3 bacterial strain at 750 mg kg(-1). Consequently, it has been concluded that PGPR has the great potential to enhance the plant growth and physiological characteristics of cowpea in Pb-contaminated sites and can also be used for bioremediation purposes.