Floral Scent Production in the Carrion Flower Genus Stapelia (Apocynacaeae)
Floral scent plays an important role in the reproductive biology of many flowering plants, often serving as a pollinator attractant. In a majority of species, floral scent is a diffuse product of the epidermis, especially that of the corolla. In some groups the production and emission of the volatile substances responsible for fragrance is localized to specialized glands, termed osmophores. This study examined the composition of floral fragrance in species of the genus Stapelia, a group of succulent perennial herbs native to the drier regions of South Africa. Volatile compounds produced by flowers were collected using headspace-solid phase microextraction. Component separation and identification was achieved using gas chromatography-mass spectrometry. A diversity of organic compounds was found among members of the genus, including various terpenoids, organic acids, sulfurous compounds, and nitrogenous compounds. Among the most common compounds were dimethyl disulfide, dimethyl trisuflide, hexanal, and trimethylamine. Although osmophores were originally described as occurring in the petals of certain milkweeds, this study has demonstrated, using a combination of vital staining and histological examination, that among Stapelia species, the production of volatile compounds appears to be a function of the corona, the often elaborate set of appendages situated between the corolla and androecium.
stapelia, plant physiology, animal-plant relationships, botany, South Africa
Souss, J. (2014). Floral scent production in the carrion flower genus stapelia (apocynacaeae) (Unpublished thesis). Texas State University, San Marcos, Texas.