VOLSKAY, ALLENA R.* and TIMOTHY P. HOLTSFORD. Division of Biological Sciences, University of Missouri, Columbia, MO 65211-7400. - Morphogenesis of Key Floral Traits in Nicotiana Section Alatae.
Nicotiana section Alatae contains species with a
surprising variety of mating systems and interactions with
pollinators, associated with variation in floral morphology. We are
exploring the development of those different floral shapes and sizes,
with a general look at perianth growth in seven species and more
detailed analyses of developmental switches in two pairs of sister
species. N. alata has a longer corolla tube than N.
forgetiana, which is important in determining which pollinators
visit the flowers. Another difference between these two is that the
stamens are adnate to the corolla for a much smaller percentage of
their length in N. forgetiana than N. alata, which may
be due at least partly to differences in cell expansion basal to the
point of filament insertion. N. longiflora and N.
plumbaginifolia flowers differ in size and anther-stigma
relationships. As the buds of N. longiflora grow and the
flowers open, the stigma remains distal to the anthers. In N.
plumbaginifolia the pistil growth slows down in relation to the
corolla and attached stamens, and just before the flower opens the
anthers pass--and deposit pollen on--the stigma. We have compared
calyx and corolla growth curves among all seven species. For the two
species pairs we are measuring cell division and expansion in the
corolla tube by mitotic index, cell length measurements, and cell
counts, and measuring growth of different locations within the corolla
and pistil by marking growing floral organs and recording the movement
of those marks. Because these traits are important to the mating
systems of these species, this research will contribute directly or
indirectly to our knowledge of floral morphogenesis, plant-pollinator
interactions, floral evolution and plant speciation.
Key words: floral evolution, morphogenesis, Nicotiana, plant morphology, pollination