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

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.

Expectations and effects of a single yoga session on pain perception

BACKGROUND Several studies show yoga may benefit chronic pain management. We investigated the effect of a single yoga session on the perception of pain, measured by a standardized pain provocation test in healthy yoga participants while also comparing pain perception to participants' own expectations. MATERIALS AND METHODS Ninety yoga participants were recruited at hatha yoga schools in Switzerland. Pain perception was measured with a standardized algometric pain provocation test; i.e., a calibrated peg was applied for 10 seconds after which the participant rated pain intensity on a 0-10 numerical rating scale. The test was applied to the middle finger, ear lobe, and second toe before and after a 60-minute yoga session. RESULTS Sixty out of 90 (66.7%) yoga participants expected a reduced pain perception after the yoga session. However, 36 (40%) participants actually experienced less pain after compared to before the yoga session. But overall, pain perception statistically did not significantly change from before to after the yoga session at any of the three body locations assessed. The expectations and also the previous yoga experience did not significantly influence the participants' pain perception. CONCLUSIONS Regardless of the high positive expectations on the influence of yoga on pain, a single yoga session does not significantly influence pain perception induced by a pain provocation test. Hypoalgesic effects of yoga should be explained otherwise.