Detection of Physiologically Active Flower Volatiles Using Gas Chromatography Coupled with Electroantennography

Abstract

Most insect-pollinated plants produce floral odour to attract their pollinators. Fragrances and floral morphology typically advertise the presence of food rewards, i.e. nectar, pollen, or oil (Vogel 1983). Floral volatiles, however, can also be the reward themselves: some euglossine bees and fruit flies actually collect the fragrance from certain flowers and thereby pollinate them (Dodson et al. 1969; Sazima et al. 1993; Tan and Nishida 2000). Some orchids emit floral odour, typically not detectable by humans, which mimics the sex pheromone of insects, the males of which pollinate the flowers in an attempted copulation or precopulatory routine (Kullenberg 1961; Peakall and Beattie 1996; Schiestl et al. 1999). These orchids exploit their pollinators as they do not provide any reward for them. On the other hand, herbivorous insects can utilise floral volatiles to find their host plants, particularly if they feed or oviposit on the flowers (Blight et al. 1995). Floral odour is thought to have originally evolved to deter insects that fed on reproductive parts of the plant (Pellmyr and Thien 1986). Accidental pollination by these insects may have outweighed the disadvantages of their feeding activity, thus leading to a selection for a means of increasing insect attraction to the flowers.