Identification of multiple stages in the conversion of maize meristems from vegetative to floral development

ABSTRACT Vegetative growth in most lines of maize is terminated at a predictable stage in development by the conversion of the shoot apical meristem into an inflorescence, the tassel. The conversion from vegetative to floral development is under developmental control, the basis of which is obscure. We have assayed the developmental potential of the shoot apical meristem in order to identify the stage at which it is determined to form a tassel. We show, using shoot apex culture, that meristems are not determined to form a tassel until after all vegetative nodes have been initiated. We also show that floral determination is a separate, later event in the development of a maize inflorescence. Intermediate stages can be distinguished in which the meristem is determinate and has the phyllotaxis of a tassel when cultured but develops vegetative shoots from buds that normally give rise to sets of florets.