Emission and Function of Volatile Organic Compounds in Response to Abiotic Stress

Abstract

Plants accumulate a diverse array of natural products, which are thought to be involved in their interactions with the environment. These chemicals function in plant communications with microbes, animals, and even other plants, as well as protecting the plant from ultraviolet radiation and oxidants. Some compounds may attract beneficial insects or microbes, whereas others kill or repel herbivorous. Many of these compounds have been referred to as “secondary metabolites” to distinguish them from the “primary metabolites” required for the growth of all plants (Theis & Lerdau, 2003). These secondary metabolites, however, are likely to be essential for successful competition or reproduction. More than 100,000 chemical products are known to be produced by plants and at least 1,700 of these are known to be volatiles (Dicke & Loreto, 2010). Some of the volatiles considered in this chapter are shown in figure 1. Volatile organic compounds (VOCs) are defined as any organic compound with vapor pressures high enough under normal conditions to be vaporized into the atmosphere (Dicke & Loreto, 2010). The importance of these compounds can be deduced by the considerable amount of photoassimilated carbon released back into the atmosphere as VOCs (Holopainen, 2004). In fact, it has been estimated that the emission of VOCs by terrestrial plants accounts for the 36% of the whole photosynthates (Kesselmeier et al., 2002). This emission, therefore, substantially reduces the amount of available carbon and consequently affects plant physiology and productivity. Why plants, under stress conditions, where carbon availability is a crucial limiting resource, lose such a relevant amount of assimilated carbon? VOCs are involved in a range of ecological functions, including indirect plant defense against insects, pollinator attraction, plant-plant communication, plant-pathogen interactions,