The effect of glucose on flower bud formation was studied in thin-layer tissue cultures of epidermal strips from flower stalks of Nicotiana tabacum L. cv. Samsun. A minimum concentration of 30 mol m−3 glucose in the MS-medium containing 1.0 mmol m−3 of both NAA and BA was necessary for flower bud formation. With 150 mol m−3 glucose a minimum stay of 10 d was required for optimal flower bud formation. Withholding glucose for a limited period at different time intervals after the onset of culture caused a delay in flower bud formation and did not affect previous development on glucose. The results indicated that competence for flower bud initiation is not restricted to the early stage of culture. The process may start at any time later at the appropriate glucose concentration. However, for both optimal initiation and further development of flower buds the presence of a metabolizable sugar is required. Incubation of the tissue on glucose is associated with higher respiration rate.