The influence of the association of barley plants with petroleum degrading bacteria on the hormone content, growth and photosynthesis of barley plants grown in the oil-contaminated soil

Maintenance of active plant growth is important for successful phytoremediation of soil contaminated with petroleum oil products. Strains of oil-degrading bacteria introduced into rhizosphere were found to reduce the extent of plant growth inhibition resulting from petroleum stress. The effect was due to combining the capacity for petroleum degradation with promotion of plant growth by bacterial phytohormones. The purpose of this work was to compare the relative importance of these mechanisms in supporting the growth of barley plants against the background of oil pollution of the soil. Plants were treated with bacterial suspensions of four strains capable of petroleum degradation and production of indole acetic acid (IAA, plant hormone of the auxin class). The strains were shown to differ in their ability to support plant growth under conditions of oil pollution. Introduction of bacteria into soil accelerated petroleum degradation. Nevertheless, oil degradation was not the only mechanism behind promotion of plant growth, since the strain with the lowest ability to degrade oil was characterized by a relatively high growth-stimulating activity. The highest ability to stimulate plant growth was detected in the case of strains, which were the most effective in increasing the concentration of IAA in plants and decreasing the stress-induced accumulation of abscisic acid (ABA).