Hydroxycinnamoyl putrescines promote the cell multiplication of leaf discs of a tobacco mutant, RMB7, cultivatedin vitro on the Murashige and Skoog medium. This mutant never accumulates these molecules during its development and does not enter in floweirng. Maximal effect is obtained at 2.5·10(-4)M. The same molecules inhibit bud formation ofNicotiana tabacum var. Xanthi nc, at 5·10(-5) M but promote callus formation. From 10(-4) M to 5·10(-3) M they strongly inhibit cell multiplication and bud formation without toxic effect. Their possible role in plant metabolism is discussed.