A developmental study of the stamens in a male-sterile tobacco hybrid

The ontogeny of the feminized stamens in a male-sterile tobacco hybrid has been studied. Plant material 1A was derived from an initial cross between Nicotiana debneyi as female and N. tabacum cv. Kupchunos as male. All 1A flowers exhibit stigmatoid anthers at anthesis and are sterile. This teratism is cytoplasmically inherited. In a developmental series of 1A floral buds, it was found that 1A stamen primordia diverge relatively early from the normal stamen shape and appear as spatulate organ rudiments lacking differentiation into anther and filament. In 1A buds after carpel fusion and as the normal stigma is differentiating, stamens form a distinctly stigmatoid tip subtended by a short filament bearing the initials of lateral outgrowths. The stigmatoid tip then enlarges to a green, bulbous recurved structure and there is considerable extension growth of the filament. Histological study of developing and mature teratological stamens showed complete absence of sporogenous tissue and also confirmed the true stigmatic nature of the tip region. The results are discussed in relation to regulation of sex determination.