The effect of introducing a supplementary ipt-gene into the genome of Nicotiana tabacum L. cv. Petit Havana SR1 is studied on the morphological plant development. The ipt-gene, accounting for the biosynthesis of cytokinins, was coupled to the heat-inducible hsp70- promoter from Drosophila melanogaster. Besides the influence of the hormonal changes involved, the effects of the experimental conditions are examined, namely the in vitro growth conditions for selecting transformed plants and the heat treatment to induce ipt-gene expression