Time of floral initiation in tobacco as a function of temperature and photoperiod

Nicotiana tabacum L. cv. Coker 319 has been found to be sensitive to changes both in temperature and photoperiod. Within a given time period fewer leaves are produced at low temperatures than at high temperatures. The classical day-neutral flowering response was not observed for this plant under six photoperiods of varying lengths. The results thus indicate that the plant may be more appropriately classified as being "preferentially ambiphotoperiodic," rather than strict "day-neutral." Preconditioning the seedlings with a long-day photoperiod produced plants that had higher total leaf numbers and flowered earlier than seedlings treated with a short-day photoperiod. The morphology of the vegetative and reproductive stem apex was similar to that reported for other species and cultivars of Nicotiana. Apical meristems were systematically ranked according to their progressive developmental stages encompassing vegetative, transition, and reproductive development.