HISTOLOGICAL-CHANGES ASSOCIATED WITH ACQUISITION OF COMPETENCE FOR SHOOT REGENERATION IN LEAF DISCS OF SAINTPAULIA-IONANTHA X CONFUSA HYBRID (AFRICAN VIOLET) CULTURED IN-VITRO

In leaf discs of Saintpaulia ionantha x confusa hybrid (cv. Virginia) cultured on shoot-inducing medium, periclinal divisions were initiated in epidermal cells 3-5 days after explant isolation. This timing coin cided with the time for competence acquisition determined in tissue-tr ansfer experiments. Some of the daughter cells from periclinal divisio ns formed the target cells which divided both anticlinally and pericli nally to form cell division centers (meristemoids), precursors of adve ntitious shoots. The target cells were not morphologically distinct fr om other epidermal cells at the light microscope level. It is suggeste d that the periclinal divisions in epidermal cells represent the dedif ferentiation phase during which target (competent) cells are formed. O nce the cells have acquired the ability to divide periclinally, both d edifferentiation and shoot induction occur in the presence of exogenou s plant hormones.