Olfactory Cues as Functional Traits in Plant Reproduction

Abstract

Floral scents are important traits which mediate interactions within biotic communities. These volatiles perform diverse functions, ranging from attracting pollinators, repelling florivores or herbivores, as well as controlling the growth of pathogens. Therefore, floral volatiles are under constant selection to balance attraction and repellence in accordance with local communities and this has led to the evolution of highly complex volatile profiles. To date, more than 1000 volatile compounds have been identified from flowers, which ultimately ensure plant reproduction by attracting pollinators. Plant–pollinator interactions mediated by floral volatiles can range from highly generalized to extremely specialized systems. By evolving exclusive relationships with pollinators that are most abundant or efficient, plants increase reproductive success. On the other hand, attracting many kinds of insects by providing generic cues and rewards leads to generalization, where plants benefit by taking advantage of pollinator diversity. Such interactions of varied strength could be achieved through tailoring different floral volatile blends. Floral scents vary widely among plants but despite the variation, there are mainly three major classes of floral volatile organic compounds (FVOCs) based on their origin, function and biosynthesis. They are terpenoids, benzenoids or phenylpropanoids, and fatty acid derivatives. Along with these, certain flowers also produce unusual compounds, which attract pollinators by mimicking food or brood sources. The production, composition, quantity and timing of volatile emissions are tightly regulated by biotic and abiotic factors that help in fine-tuning the ecological interactions mediated by FVOCs. This chapter updates the current knowledge on these aspects and emphasizes the ecological importance of floral volatiles. Further, the various methods for collection and analyses of FVOCs are also described.