The Possible Role of Zearalenone in the Floral Gradient in Nicotiana tabacum L.

Abstract

Summary After plants entered the reproductive stage, the buds of a day-neutral tobacco (Nicotiana tabacum L. cv. Samson) developed in situ according to the following characteristic order: the apical bud, the lateral buds and three to four axillary buds below the apical bud produced inflorescences first, the next one or two lower axillary buds remained quiescent. The bud just below this zone developed predominantly into a floral branch. If the plant was allowed to grow in favorable conditions, the axillary buds located below the predominantly-developing-floral-branch (PDF) also remained quiescent and another axillary bud just below these quiescent buds developed predominantly. Such a growth model of axillary buds was expressed in the axillary buds of PDF and plants that were decapitated. The distribution of endogenous zearalenone (ZEN) in the stem was in correlation to this model, that is, there were higher levels of ZEN in the nodes at the upper side of which the predominantly-developing-bud (PDB) was located than the nodes at the lower side of which the same PDB was located. The results suggested that ZEN may be one of the important floral stimuli of day-neutral tobacco and is related to the floral gradient in tobacco shoot.