Floral scents are most often emitted by the petals, but other floral parts may also play a role in scent production and scent emission (Dobson, 1994). Pollen odors are considered in evolutionary terms to be the oldest olfactory attractants in flowers (Faegri and van der Pijl, 1979). They probably evolved as defense compounds against pollen-feeding animals and pathogens (Pellmyr and Thien, 1986). However, when plants became dependent on animals as pollen vectors, some attractive compounds were included among pollen volatiles (Dobson and Bergström, 2000).

Ranunculus acris	Trollius europaeus	Caltha palustris	Pulsatilla vulgaris

Aquilegia sylvestris	Aquilegia chrysantha	Anemone sylvestris

Odors of the androecium and in particular of pollen have shown to be species-specific and to differ quantitatively and/or qualitatively from other floral parts (von Frisch, 1923; von Aufsess, 1960; Buchmann, 1983; Dobson, 1987; Dobson et al., 1990, 1996; Dobson and Bergström, 2000). 

Pollen volatiles have been of special interest in relation to pollen collecting bees as important cues for flower discrimination (Dobson, 1987, 1991), for example, generalist honeybees having the ability to distinguish between pollen odors of different plant taxa (Doull, 1966), and pollen specialist bees using floral and pollen fragrances to locate their specific host plant (Dobson, 1987).

Pollen odors in Ranunculaceae

Thermal desorption of anthers in quartz microvials inserted into a modified injector was used to investigate anther volatiles of 12 Ranunculaceae species distributed in six genera: Anemone, Aquilegia, Caltha, Pulsatilla, Ranunculus, and Trollius. 

Chemical analysis (GC-MS) yielded a total of 116 compounds from which 103 compounds could be identified. A great diversity of compounds was observed, including aliphatic compounds, aromatics, mono- and sesquiterpenoids, and nitrogen-bearing compounds. Intraspecific variation in the chemical profiles was significantly lower than interspecific variation. Eight compounds explained 96.1% of the observed total variation between the taxa: protoanemonin, octanal, (E,E)-α-farnesene, 2-phenyl ethanol, pentadecane, α-muurolene, phenyl acetaldehyde, and linalool oxide (pyranoid) were either present only in specific taxa or varied greatly in their relative amount between the taxa. 

An analysis of the scent data using the CNESS distances of chemical profiles of the species, followed by visualization of the data with nonmetric multidimensional scaling (NMDS) showed that most species belonging to the same genus have similar chemical compositions.

Bergström, G., H. E. M. Dobson, and I. Groth 1995. Spatial fragrance patterns within the flowers of Ranunculus acris (Ranunculaceae). Plant Systematics and Evolution 195: 221-242.

Buchmann, S. L. 1983. Buzz pollination in angiosperms. In C. E. Jones and R. J. Little [eds.], Handbook of Experimental Pollination Biology, 73-113. Academic Press, New York, New York, USA.

Dobson, H. E. M. 1987. Role of flower and pollen aromas in host-plant recognition by solitary bees. Oecologia 72: 618-623.

Dobson, H. E. M. 1994. Floral volatiles in insect biology. In E. A. Bernays [ed.], Insect-Plant Interactions, vol. 5, 47-81. CRC Press, Boca Raton, Florida, USA.

Dobson, H. E. M. 1991. Pollen and flower fragrances in pollination. In C. Van Heemert and A. De Ruijter [eds.], Proceedings of the 6th international symposium on pollination, Tilburg 1990. Acta Horticulturae 288: 313-320. 

Dobson, H. E. M., G. Bergström, and I. Groth, 1990. Differences in fragrance chemistry between flower parts of Rosa rugosa. Israel Journal of Botany 39: 143-156.

Dobson, H. E. M., I. Groth, and G. Bergström 1996. Pollen advertisement: chemical contrasts between whole-flower and pollen odors. American Journal of Botany 83: 877-885.

Dobson, H. E. M., and G. Bergström 2000. The ecology of pollen odors. Plant Systematics and Evolution 222: 63-87.

Doull, K. M. 1966. The relative attractiveness to pollen-collecting honeybees of some different pollens. Journal of Apicultural Research 5: 9-14.

Faegri, K., and L. van der Pijl 1979. The Principles of Pollination Ecology, 3rd edn. Pergamon Press, Oxford, Great Britain.

Pellmyr, O., and L. B. Thien 1986. Insect reproduction and floral fragrances: keys to the evolution of the angiosperms? Taxon 35: 76-85.

von Aufsess, A. 1960. Geruchliche Nahorientierung der Biene bei entomophilen und ornithophilen Blüten. Zeitschrift für Vergleichende Physiologie 43: 469-498.

von Frisch, K. 1923. Über die "Sprache" der Bienen. Zoologische Jahrbücher – Abteilung für Allgemeine Zoologie und Physiologie der Tiere 40: 1-186.

_{Andreas Jürgens}