Auxin formation by rhizosphere bacteria as a factor of root growth

Abstract
Bacteria of the speciesPseudomonas putida andPseudomonas fluorescens isolated from the rhizosphere of maize and bean plants produce indol-3-ylacetic acid and some other auxins when grown in suspension cultures. IAM and ILA were also found besides IAA and its degradation product IAH by means of HPLC and MS methods. This finding indicates the involvement of two different metabolic pathways in IAA synthesis in bacteria. The amounts found varied between 1.6 and 3.3 μg IAA per ml of media which corresponded to 100–200 μg per gram of bacterial dry mass. The effect of IAA production by rhizosphere bacteria on IAA level in the plant is discussed.