title: The composition and timing of flower odour emission by wild Petunia axillaris coincide with the antennal perception and nocturnal activity of the pollinator Manduca sexta.
abstract: In the genus Petunia, distinct pollination syndromes may have evolved in association with bee-visitation (P. integrifolia spp.) or hawk moth-visitation (P. axillaris spp). We investigated the extent of congruence between floral fragrance and olfactory perception of the hawk moth Manduca sexta. Hawk moth pollinated P. axillaris releases high levels of several compounds compared to the bee-pollinated P. integrifolia that releases benzaldehyde almost exclusively. The three dominating compounds in P. axillaris were benzaldehyde, benzyl alcohol and methyl benzoate. In P. axillaris, benzenoids showed a circadian rhythm with an emission peak at night, which was absent from P. integrifolia. These characters were highly conserved among different P. axillaris subspecies and P. axillaris accessions, with some differences in fragrance composition. Electroantennogram (EAG) recordings using flower-blends of different wild Petunia species on female M. sexta antennae showed that P. axillaris odours elicited stronger responses than P. integrifolia odours. EAG responses were highest to the three dominating compounds in the P. axillaris flower odours. Further, EAG responses to odour-samples collected from P. axillaris flowers confirmed that odours collected at night evoked stronger responses from M. sexta than odours collected during the day. These results show that timing of odour emissions by P. axillaris is in tune with nocturnal hawk moth activity and that flower-volatile composition is adapted to the antennal perception of these pollinators.
authors.affiliation: Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland.
authors.forename: Maria Elena
authors.initials: ME
authors.lastname: Hoballah
authors.forename: Jeroen
authors.initials: J
authors.lastname: Stuurman
authors.forename: Ted C J
authors.initials: TC
authors.lastname: Turlings
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Guerin
authors.forename: Sophie
authors.initials: S
authors.lastname: Connétable
authors.forename: Cris
authors.initials: C
authors.lastname: Kuhlemeier
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D003624:Darkness; D035264:Flowers / Q000737:chemistry / Q000502:physiology*; D018402:Manduca / Q000033:anatomy & histology* / Q000502:physiology*; D009812:Odorants / Q000032:analysis*; D032306:Petunia / Q000737:chemistry / Q000502:physiology*; D011058:Pollen / Q000502:physiology