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.