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