Spring Wheat Yield under Application of Growth-Promoting Rhizobacterium in Soil Contaminated with Nickel

The impact of growth-promoting rhizobacterium Pseudomonas fluorescens 20 on the yield of spring wheat was studied in a pot experiment. Plants were grown up to maturity when agrogray soil was contaminated with Ni as NiCl 2 ·6H 2 O at a rate of 200 mg Ni/kg of soil against the background of applying NPK fertilizers. After harvesting, the content of nutrients N, P, K, Ca, Mg, Fe, Mn, Zn, and Cu in grain, straw, and roots was determined. N was determined by the phenol technique. Resistance of plants to Ni toxicity was found under bacterial inoculation. Application of bacterium eliminated phytotoxicity of heavy metal and provided the same biomass production, including grain, as in control (noninoculated plants not exposed to Ni stress). Resistance of plants inoculated with bacterium to Ni toxicity was due to enhanced growth of the root system and increase in content and accumulation of Ni in roots and, as a result, this was not accompanied by increase in metal incorporation into aboveground organs. The application of bacterium also improved mineral nutrition of plants and increased nutrient uptake from contaminated soil. Increase in nutrient uptake by yield from contaminated soil as influenced by inoculation with bacterium was due to growth promotion and increase of plant weight in general without significant changes in the content of most elements in aboveground organs and roots. Bacterium enhanced phytoextraction of heavy metal (soil cleaning) and increased Ni uptake by aboveground organs without significant changes in its content in grain and straw. Increase in Ni uptake by bacterially inoculated plants occurred without changes of soil medium reaction and was probably due to production of bacterial siderophores.