Studies on the Initial Process of Adventitious Bud Differentiation in Torenia Stem Segments Cultured in vitro I. Effects of Cytokinin

Abstract

Summary The effects of mineral nutrients and growth regulators added to culture medium on the initial stages of adventitious bud differentiation were investigated using Torenia internodal segments cultured In vitro. Meristematic zones (MZ) appeared prior to adventitious bud formation in the epidermal Cell layers of stem segments. Adventitious bud and Mz formation was rarely noted in the explants Cultured on the MS medium without benzyladenine (BA). When explants were cultured on a medium composed of only BA and sucrose, MZ were formed but no adventitious bud initiation was observed. While, both MZ and bud formation was strongly promoted when a medium consisting of mineral nutrients and BA was used. Applications of indole-3-acetic acid and gibberellic acid stimulated neither MZ nor bud formation. When explants were cultured on a medium containing only BA (1.0 mg/l) and sucrose during the first 6 d and then transferred to nutrient medium without BA, adventitious buds were differentiated at a high rate. Consequently, it seems that BA strongly promoted MZ formation (bud initiation) during initial period of culture and mineral nutrients play major role in subsequent development of MZ to bud primordia.