The abilities of nine transconjugants of Pseudomonas putida BS1380 and P. aureofaciens BS1393 carrying various plasmids of naphthalene biodegradation to synthesize the phytohormone indolyl-3-acetic acid (IAA) were studied, All transconjugants synthesized high levels of IAA in comparison to parent strains, P. putida BS1380 carrying the pBS3 plasmid synthesized the highest level of the phytohormone. Our studies did not find any known pathways of IAA synthesis on plasmids of naphthalene biodegradation, Direct effects of IAA synthesized by the P. putida BS1380 (pBS3) transconjugant on the formation of root systems of green cuttings of black currant and cherry plants were shown.