MORPHOMETRIC ANALYSIS OF THE GROWTH OF PHSP70-IPT TRANSGENIC TOBACCO PLANTS

The effect of introducing a supplementary ipt-gene into the genome of Nicotiana tabacum L. cv. Petit Havana SR1 is studied on the morphologi cal plant development. The ipt-gene, accounting for the biosynthesis o f cytokinins, was coupled to the heat-inducible hsp70- promoter from D rosophila melanogaster. Besides the influence of the hormonal changes involved, the effects of the experimental conditions are examined, nam ely the in vitro growth conditions for selecting transformed plants an d the heat treatment to induce ipt-gene expression. The phenotype of t he plants is determined by the tissue sensitivity to three factors: (1 ) heat treatment reduces stem elongation and diameter growth; (2) in v itro pre-cultivation also reduces stem elongation; and (3) expression of the ipt-gene stimulates diameter growth, induces debudding of the a xillary shoots and inhibits root development. In addition, axillary bu d development indicates that in vitro cultivation affects ipt-gene exp ression.