Differences between Dianthus caryophyllus L cultivar in in vitro growth and morphogenesis are related to their ethylene production

The involvement of ethylene in the vitro development of shoots from nodal s egments of two cultivars of carnation (Dianthus caryophyllus L.) was studie d. Shoots of cv. Barbaret Antares showed low hyperhydricity in contrast wit h the high levels showed by cv. Barbaret Tanga when both were cultured in a irtight culture vessels. Longer shoots were produced, in both cases, when t he rate of gas exchange in the culture vessel was increased by using vented closures, which also prevented hyperhydricity and increased the multiplica tion coefficient in cultures of Barbaret Tanga. The two cultivars produced ethylene throughout the culture period but, a hi gher amount was produced during the first, second and fourth weeks in cultu re by the cultivar more sensitive to ventilation (Barbaret Tanga). Trapping ethylene did not produce any effect on cv. Barbaret Antares but improved t he quality of cv. Barbaret Tanga explants, decreasing hyperhydricity and in creasing the number of shoots, the length of the main shoot and the multipl ication coefficient. These effects were more marked when ethylene was trapp ed during the first two weeks in culture.