Changes in cytokinin activities before, during and after floral initiationin Polianthes tuberosa

The contents of endogenous cytokinin in tuberose corms (Polianthes tuberosa ) at vegetative, early floral initiation, and flower development stages wer e investigated. We also determined the influence of exogenous cytokinin tre atment on the corm apex at three different growth stages in relation to flo ral initiation and development in tuberose. The exogenous cytokinin effecti vely induced floral initiation and development, especially at the early flo ral initiation and flower development stages. Endogenous cytokinins were hi gher in early floral initiation and development stages in comparison to the vegetative stage. During floral initiation stage, the zeatin and dihydroze atin increased significantly, while the cytokinins, zeatin riboside, dihydr ozeatin riboside, N-6-(delta(2)-isopentenyl) adenine, and N-6-(delta(2)-iso pentenyl) adenine riboside at consistently low levels. The increase of cyto kinin levels in tuberose corms during floral induction suggests a role for cytokinins in tuberose apex evocation. Moreover, these results indicate tha t cytokinins seem to promote the development of flower buds rather than ind ucing flowering in tuberose. (C) 1999 Editions scientifiques et medicales E lsevier SAS.