Inoculation of canola seeds with Pseudomonas putida GR12-2 stimulates root elongation under gnotobiotic conditions. Transformation of P. putida GR12-2 with the broad-host-range plasmid pGSS15 abolishes the enhancement of root elongation. With scanning electron microscopy it was found that both transformed and nontransformed P. putida GR12-2 are capable of binding to canola seed coats. In addition, it was observed that 4 days after the initial inoculation the roots of both P. putida GR12-2- and GR12-2/pGSS15-treated seedlings were free of adhering bacteria despite the fact that it was subsequently shown that both bacterial strains are capable of binding to roots. Thus, adhesion to roots is not necessary for the initial phase of enhanced root elongation that is induced by P. putida GR12-2 under gnotobiotic conditions.