Growth and Mineral Nutrition of Spring Wheat Inoculated with Plant Growth Promoting Rhizobacterium in Soil Contaminated with Nickel

Abstract

A greenhouse experiment was conducted to study the effect of the plant growth promoting rhizobacterium Pseudomonas fluorescens 20 on spring wheat productivity in agrogray soil artificially contaminated with a water-soluble nickel compound. Plants were grown until the booting stage; NPK fertilizers and NiCl₂⋅6H₂O were applied to soil. The contaminant application rate was 300 mg Ni/kg soil, which significantly exceeds its maximum permissible concentration in soils. The chemical composition of plants and the uptake of nickel and nutrients from soil by shoots and roots were examined. Concentrations of Ni and other ash elements were determined after wet combustion of plant samples using inductively coupled plasma optical emission spectrometry and flame photometry. The nitrogen content in plants was determined using the phenol method. Bacterial inoculation increases the resistance of plants to toxic effects of the heavy metal, which is expressed in the higher weight of their vegetative organs and roots in contaminated conditions. Simultaneously the mineral nutrition of spring wheat improves, and the from soil by the plants increases; apparently, this manifests their protective response to soil contamination with Ni. The general growth promotion observed in bacterially inoculated plants is not accompanied by significant changes in the content of elements in their shoots and roots. The application of the bacterium intensifies Ni phytoextraction from soil (i.e., soil purification from the heavy metal) and the Ni uptake by roots without significant changes in its concentration in shoots and roots. The amounts of metal accumulated in roots exceed those accumulated in shoots by an order of magnitude. Regardless of bacterial inoculation, soil contamination with Ni increases the content of Mg and some other nutrients in shoots and roots of plants.