Axillary Bud Differentiation Research Articles

Morphological observation on vegetative growth and flower bud formation in Oncidium Boissiense

The growth habit, axillary bud differentiation, pseudobulb development and flower bud formation in Oncidium Boissiense, a sympodial orchid hybrid, were observed from 24 January to 2 October 1980. The axillary bud on the basal part of the latest back-bulb (last year's growth) started to develop new growth (the “lead”) in early spring. The upper portion of the lead swelled to form a pseudobulb. The pseudobulb development started on 20 March and terminated between early July and early August. At the early stage of the lead development, four axillary buds had already differentiated at the axils of the basal sixth or seventh node and upwards. The uppermost bud started to elongate after mid-May, and developed into a flower-stalk. Branch formation in the axil of the bract on the flower stalk was observed in mid-May. Floret bracts were formed on the branches in mid-June. Floret primordia were differentiated at the axils of these bracts in early-July. Florets developed to the pollen-formation stage by 25 September and bloomed in mid-October 1980. Possible factors affecting flower-stalk development and floret initiation of this hybrid are discussed.

HORMONAL REGULATION OF FLOWERING IN A SYMPODIAL ORCHID HYBRID DENDROBIUM LOUISAE

SummaryThe growth habit, axillary bud differentiation and flowering behaviour in a sympodial orchid hybrid, Dendrobium Louisae cv. ‘Dark’ were studied. Flowering occurred only after termination of vegetative growth in the pseudobulb. Intermediate shoots with both vegetative and reproductive growth were produced when plants were placed in the shade. Decapitation did not stimulate floral initiation. In mature pseudobulbs, Cytokinin (benzyladenine) stimulated flowering. Gibberellic acid enhanced the cytokinin effect but was itself not effective. It is suggested that flowering in this orchid hybrid is regulated by growth substances, both qualitatively and quantitatively.