Effects of some growth regulators on in vitro flowering of Streptocarpus nobilis.

Leaf discs from vegetative Streptocarpus nobilis plants were cultured in vitro in media with cytokinin (BAP or K at 0.35 mg.1(-1)) and auxin (IAA, NAA or 2,4-D at 0.1 mg.1(-1)). Under short days (8-h photoperiod) in medium with IAA and BAP, floral buds developed in 100% of the cultures; under long days (16-h photoperiod) only shoots were formed. In medium with IAA and K, flowering was reduced. Flowers rarely formed in medium containing NAA and K, but roots developed profusely. NAA + BAP promoted leafy shoots which rarely flowered later. The effect of 2,4-D was to inhibit flowering completely and to induce callusing and formation of teratomous structures.