ACQUISITION OF COMPETENCE FOR SHOOT REGENERATION IN LEAF DISCS OF SAINTPAULIA-IONANTHA X CONFUSA HYBRIDS (AFRICAN VIOLET) CULTURED IN-VITRO

Leaf discs from Saintpaulia ionantha x confusa hybrids (African violet ) were transferred between basal medium (BM) containing no hormones an d shoot-inducing medium (SIM) containing 2.0 mg l(-1) indole acetic ac id and 0.08 mg l(-1) 6-benzylaminopurine to determine whether there is a ''window'' of competence for shoot regeneration. Leaf discs precult ured on BM prior to transfer to SIM formed buds 3 days earlier than th e controls (leaf discs not precultured) regardless of whether the disc s were placed upside down or right side up on the medium. This suggest s that cultured leaf cells were not competent for shoot induction duri ng the first 3 days of culture. Leaf discs cultured right side up (aba xial surface to the medium) did not form buds on BM alone, unlike disc s cultured upside down. Leaf disc survival was affected by a delay in hormonal exposure, but surviving leaf discs produced as many shoots as control leaf discs. This suggests that in the absence of exogenous pl ant hormones, cellular competence to regenerate shoots is not lost in excised leaf discs of African violet.