Development Of Staminate Flowers Research Articles

Comparative development of staminate and pistillate flowers in the dioecious cactus Opuntia robusta.

PCD role in unisexual flowers. The developmental processes underlying the transition from hermaphroditism to unisexuality are key to understanding variation and evolution of floral structure and function. A detailed examination of the cytological and histological patterns involved in pollen and ovule development of staminate and pistillate flowers in the dioecious Opuntia robusta was undertaken, and the potential involvement of programmed cell death in the abortion of the sex whorls was explored. Flowers initiated development as hermaphrodites and became functionally unisexual by anthesis. Female individuals have pistillate flowers with a conspicuous stigma, functional ovary, collapsed stamens and no pollen grains. Male individuals have staminate flowers, with large yellow anthers, abundant pollen grains, underdeveloped stigma, style and an ovary that rarely produced ovules. In pistillate flowers, anther abortion resulted from the premature degradation of the tapetum by PCD, followed by irregular deposition of callose wall around the microsporocytes, and finally by microspore degradation. In staminate flowers, the stigma could support pollen germination; however, the ovaries were reduced, with evidence of placental arrest and ovule abortion through PCD, when ovules were present. We demonstrate that PCD is recruited in both pistillate and staminate flower development; however, it occurs at different times of floral development. This study contributes to the understanding of the nature of the O. robusta breeding system and identifies developmental landmarks that contribute to sexual determination in Cactaceae.

Polyaxial development in homeotic flowers of three begonia cultivars

Development of staminate flowers in double-flowering Begonia semperflorens-cultorum cultivars 'Cinderella', 'Goldie Locks', and 'Lucy Lockett' was examined using epi-illumination microscopy, focussing on later stages when secondary partial floral buds formed on the floral apex. This process, switching from floral to inflorescence-like development, is an example of homeosis, the expression of inflorescence features on a floral apex. Floral development began as in a normal begonia flower with the formation of a perianth consisting of two sepals and two petals, but sepaloid and (or) petaloid appendages then developed in what corresponded to stamen positions in normal Begonia species. This was usually followed by lateral elongation, distortion of the primary floral apex, and formation of secondary partial floral buds. The pattern of primordial inception on the secondary apices tended to be irregular, but in some cases, appendage primordia formed in groups of twos, threes, and fours, and in a somewhat alternating formation on the apices. Often, primordial initiation seemed to continue on secondary apices even after anthesis of the staminate flower. Appendage primordia that formed on the secondary buds usually were laterally elongate and bifacial, giving them a phyllomic appearance. Others were, on occasion, more hemispherical at inception, but as they developed they became phyllomic. Key words: homeosis, polyaxial, floral development, intermediate inflorescence.

The Morphology of Staminate Flower Differentiation in Pecan

Abstract Inflorescence and staminate flower development in pecan [Carya illinoinensis (Wang.) K. Koch] were examined using scanning electron microscopy. Organogenesis was described from inception to pollen dehiscence. The order of organ initiation was: a single bract, rounded floral apex, 2 lateral bracteoles, and 3-7 stamens. The initiation and time when stages of floral differentiation occur were determined for 1 protandrous and 2 protogynous cultivars. The time of early inflorescence development and the initiation of floral primordia and bracts were similar in both cultivar types, occurring about 12 months prior to staminate maturity. However, the initiation time of later floral development stages was divergent. The floral stages in the protandrous cultivar up to anther lobing occurred during the previous growing season. In the protogynous cultivars, initiation of bracteoles, the floral apex, stamen primordia and anther lobing took place in the spring of their anthesis.