Plant Volatiles

Abstract

Plants produce an amazing number of chemical compounds that can disperse in the air at ambient temperature. These plant volatiles have served mankind, perhaps since pre‐Neolithic times, as perfumes and flavour compounds. In nature, these compounds attract pollinators and seed dispersers, protect plants through repulsion or intoxication of attacking herbivores, entice predator or parasitoid insects that prey on herbivores, prime defences of neighbouring plants against imminent attack, confer antimicrobial properties critical to defence against pathogens, and mitigate oxidative stresses. Plant volatiles are typically classified into four major categories: terpenoids, fatty acid derivatives, amino acid derivatives and phenylpropanoid/benzenoid compounds, though a number of species‐ or genus‐specific volatile compounds, such as those found in select species of Alliaceae and Brassicaceae, fall outside these categories. This enormous variety is represented by more than 1700 compounds from 90 species. Key Concepts: Plant volatiles are critical in the attraction of pollinators and seed dispersers. Plants use volatiles to protect themselves from pests and pathogens. Plants under herbivore attack can alert neighbouring plant species, priming their chemical defences. Plant volatiles are classified according to their metabolic origins as terpenoids, phenylpropanoids/benzenoids, fatty acid derivatives and amino acid derivatives. Biosynthesis of plant volatiles is spatially, developmentally and temporally regulated. Modern techniques for the collection and trapping of plant volatiles (SPME, dynamic headspace sampling) provide sensitive and representative samples for analysis. Plant volatiles serve humankind as perfumes and aroma compounds, natural flavour constituents, food additives/preservatives, and chemotherapeutics and anaesthetics.

Fruit aromas in mature fleshy fruits as signals of readiness for predation and seed dispersal

“…It has been proposed that the different VOCs could act synergistically, as in conifer resins, for simultaneous protection against pests and pathogens (Phillips & Croteau, 1999). Recent data have demonstrated that VOCs serve as signals for communication between plants and between distal parts within the same plant (Qualley & Dudareva, 2001). They are also involved in protecting the plant against abiotic stress, defending the plant against pests and pathogens, and attracting herbivore predators and pollinators (Gershenzon & Dudareva, 2007;Kessler et al, 2008).…”

“…This group comprises short chain (C6) acyclic aldehydes, alcohols and their esters produced by plants from most taxa as a wound response via the enzymatic metabolism of polyunsaturated fatty acids. However, species-or genus-specific VOCs have been described in some species, such as the sulfur-containing VOCs of Alliaceae and Brassicaceae (Qualley & Dudareva, 2001). To understand the functional significance of VOCs in ripe fruits, it is necessary to know their biosynthesis and developmental regulation, their quantitative and qualitative accumulation and the responses triggered by VOCs on organisms interacting with the fruit, including vertebrates, insects and microorganisms.…”

Structural variation underlies functional diversity at methyl salicylate loci in tomato

“…The volatiles emitted from flowers allow plants to attract and guide pollinators to ensure fertilization and reproduction [1,2], whereas aroma from fruits allure frugivores to assist in seed dispersal [3][4][5] and fend off pre-and post-harvest diseases [5][6][7]. Volatiles play important roles in intra-and inter-plant communications as these compounds facilitate the signaling about the danger to distant parts of same or to neighboring plants [8,9]. Furthermore, volatiles can act as direct defenses, either by repelling the danger [10,11], or intoxicating herbivores and pathogens [12,13].…”