Plant growth substances produced by microorganisms of the rhizosphere and the soil

Microorganisms isolated from the soil and the rhizosphere of wheat plants produce growth regulating substances with effects similar to gibberellins when grown in submerse cultures. Bioassays and thin layer chromatography were used for characterization. Different plant growth regulating substances and variations in their quantity were observed among microorganisms. The amounts of gibberellin-like substances found in culture filtrates varied, in a range from 0.01 to 1.0 mg GA₃ equivalents per liter.