Developmental physiology of floral initiation inNicotiana tabacumL.

Abstract

The central process in the making of a multicellular organism is the fating of cells and tissues for their terminal phenotypes. The formation of a flower from a shoot apical meristem completes a sequence of fating processes initiated in embryogenesis. The fating of a vegetative meristem of Nicotiana tabacum L. to initiate a flower involves at least two signals and two developmental states. A signal from the roots maintains vegetative growth, or prevents flowering, in the young seedling. As the plant grows, the vegetative meristem gains greater competence to respond to the floral stimulus from the leaves until it is evoked, by floral stimulus, into a florally determined state. The florally determined state is then expressed. These developmental processes not only establish the time of floral initiation, but also regulate plant size as measured by the number of nodes produced.