Spatial fragrance patterns within the flowers ofRanunculus acris (Ranunculaceae)

Floral scents emitted from different flower parts ofRanunculus acris were investigated by trapping headspace volatiles onto Porapak Q followed by solvent desorption and GC-MS analysis. Isoprenoids, strongly dominated bytrans--ocimene, constituted the principal class of volatiles in all flower parts except pollen; sesquiterpenes were especially diverse. Odors collected separately from petals, stamens, and sepals + gynoecium comprised the same volatiles, but these were present in disparate proportions among the flower parts, thereby creating subtle contrasts within the flower. The main sources of volatiles were the petals and stamens, which made equal contributions to the whole-flower fragrance. Emissions from the petals differed quantitatively between the apical and basal petal regions, thereby paralleling optical nectar-guide patterns. Pollen odor was markedly unlike that of other flower parts, with only few volatiles, a high representation of 5-methylene-2(5H)-furanone (protoanemonin), and no detectabletrans--ocimene. The distinctiveness of the pollen's volatile profile suggests that it may serve a signalling role to pollen-feeding insects.