Response of tobacco plants transformed with the ipt gene to elevated temperature

Transpiration rates and the content of ABA and cytokinins were compared in wild-type tobacco (Nicotiana tabacum L.) plants and the transgenic plants c arrying the ipt gene, which codes for isopentenyltransferase and is express ed after a heat-shock treatment. The heat treatment initially stimulated th e transpiration rate in plants of both groups. This stimulation was followe d by a decrease in the transpiration of wild-type plants, whereas the trans piration rate remained high in transgenic plants. The heat shock promoted t he accumulation of cytokinins in transgenic plants but had little effect on the cytokinin content in wild-type plants. The concentration of ABA increa sed after the heat shock in both plant groups. The significance of elevated cytokinin content for maintaining high transpiration rates in transgenic p lants is discussed.