AUTOFLUORESCENT WALLS OF CONNECTIVE BASES IN ANTHERS OF BARNADESIOIDEAE (ASTERACEAE), AND SYSTEMATIC IMPLICATIONS

Stamens from 20 species of the subfamily Barnadesioideae were examined with confocal scanning laser microscopy to determine some of the char acteristics of the connective base epidermis. All species had autofluo rescent cell walls. Wall autofluorescence was more intense in the abax ial connective epidermis than in the filament epidermis. In most speci es all autofluorescent cell walls were evenly thickened, but in severa l species of Barnadesia some either had spiral thickenings or were irr egularly thickened, perhaps an adaptation for increased strength in lo nger filaments and anthers as part of a hummingbird pollination syndro me, a derived condition within the subfamily. In slightly less than ha lf the species the connective base exhibited a more intense autofluore scence than any other region of the connective. The adaxial epidermis was autofluorescent in eight species. The occurrence of autofluorescen t cells in both Calyceraceae and Barnadesioideae suggests this as a po ssible synapomorphy, but in the former the cells are tangentially elon gate and irregular, rather than longitudinally elongate with rectangul ar outline.