Conditions leading to flower formation on excised Begonia fragments cultured

Fragments of leaves, petioles and floral stalks of several species and varieties of Begonia have been cultured in vitro on denned media. The presence of a cytokinin, adenine and an auxin was found necessary for optimum bud formation, especially on petioles and floral stalks. Flower buds could be produced on leaves and floral stalks, but not on petioles. They were of the male type. As early as 1892 SACHS (1) reported that cuttings taken from flowering begonias regenerated plants which flowered much earlier than plants regenerated from begonias which were still vegetative. This observation led him to postulate the existence of a special flower-forming principle. In recent years, it has been possible to obtain the de novo formation of flower buds on fragments of stems, leaves and roots cultured in vitro (see review articles 2-5). Using such aseptic techniques, we have tried to get some information about the conditions under which flower buds can be induced to form on excised fragments of leaves, stems, petioles and floral stalks of various species and varieties of Begonia. Materials and methods Plant material The species and varieties used were Begonia x cheimantha "Gloire de Lorraine " and "Regent", B. teuscheri x coccinea "Corallina de Lucerna" It is a real pleasure to express our gratitude to Professor Dr. von DENFFER who gave the initial impetus for this piece of research and granted a leave of absence to Dr. F. RINGE in order to originate the in vitro culture of Begonia species in the Laboratoire de Physiologie Pluricellulaire at Gif-sur-Yvette