Abstract

The structure and histogenesis of the stigma of Datura stramonium was investigated by light and scanning electron microscopy to determine the developmental origin of the transmitting tissue and “wet stigma”. Four developmental stages were defined on the basis of bud length. Stage one, the histogenesis stage, was comprised of buds 2-15 mm in length. Stage two, signified by the growth and development of the stigma was comprised of buds 15-40 mm long. Stage three, with buds of 40-60 mm in length, represented a receptive and mature stigma. Stage four started with self pollination (occurs prior to anthesis) and ended with stigma senescence. A developing stigma showed a bilobed, papillated surface, covered with sticky secretion. The stigma consisted of two distinct zones; 1) Superficial zone; formed by papillae and 5-8 layers of secretory cells immediately beneath them. This zone was subjected to a gradual lysis in the ontogeny of the stigma. 2) Internal zone; formed by the transmitting tissue of the style. This zone remained intact throughout the development. Transmitting tissue and stigma both originated from the epidermis of the carpels. Similarities in structural organization of the stigma of Datura to those reported in Solanum tuberosum were considerable.