Induction of early flowering in Cymbidium niveo-marginatum Mak in vitro

Many orchids take several years to flower. We have been able to induce earl y flowering in the temperate orchid Cymbidium niveo-marginatum Mak in vitro . The combined treatment of cytokinin (6-benzylaminopurine), restricted nit rogen supply with phosphorus enrichment, and root excision (pruning) induce d transition of the Cymbidium shoot from a vegetative to a reproductive sta ge. Nearly 100% of the plants flowered within 90 days only when the combine d treatment was applied. When root excision and/or 6-benzylaminopurine were omitted from the combined treatments, flower induction was significantly r educed. The auxin transport inhibitor, 2,3,5-triiodobenzoic acid prevented flowering of Cymbidium in vitro, although auxin (a-naphthaleneacetic acid) itself did not induce flowering. Gibberellic acid markedly delayed flowerin g in C. niveo-marginatum even when the flower-promoting treatment was appli ed. Paclobutrazol, an anti-gibberellin agent, totally blocked the inductive effects of either cytokinin or pruning. These observations suggest that co ncerted actions of auxin, cytokinin, and gibberellin, as well as nutrient c oncentration and putative promoting/suppressing agents, determine the timin g of Cymbidium orchid transition from the vegetative to reproductive stage.