Ozone Degrades Common Herbivore-Induced Plant Volatiles: Does This Affect Herbivore Prey Location by Predators and Parasitoids?

Abstract

Inducible terpenes and lipoxygenase pathway products, e.g., green-leaf volatiles (GLVs), are emitted by plants in response to herbivory. They are used by carnivorous arthropods to locate prey. These compounds are highly reactive with atmospheric pollutants. We hypothesized that elevated ozone (O(3)) may affect chemical communication between plants and natural enemies of herbivores by degrading signal compounds. In this study, we have used two tritrophic systems (Brassica oleracea-Plutella xylostella-Cotesia plutellae and Phaseolus lunatus-Tetranychus urticae-Phytoseiulus persimilis) to show that exposure of plants to moderately enhanced atmospheric O(3) levels (60 and 120 nl l(-1)) results in complete degradation of most herbivore-induced terpenes and GLVs, which is congruent with our hypothesis. However, orientation behavior of natural enemies was not disrupted by O(3) exposure in either tritrophic system. Other herbivore-induced volatiles, such as benzyl cyanide, a nitrile in cabbage, and methyl salicylate in lima bean, were not significantly reduced in reactions with O(3). We suggest that more atmospherically stable herbivore-induced volatile compounds can provide important long-distance plant-carnivore signals and may be used by natural enemies of herbivores to orientate in O(3)-polluted environments.

Changes in the volatile profile of Brassica oleracea due to feeding and oviposition by Murgantia histrionica (Heteroptera: Pentatomidae)

“…This contrasts with other systems involving the same plant species attacked by chewing insects (Mattiacci et al, 2001b;Fatouros et al, 2005;Bukovinszky et al, 2005;Geervliet et al, 1997;Pinto et al, 2007) or other plant species attacked by piercingsucking insects (Rodriguez-Saona et al, 2002;Colazza et al, 2004b). This inconsistency might be due to the infestation level (Dicke et al, 1993;Tumlinson et al, 1993), which was very low in the case of air entrainments from B. oleracea attacked by M. histrionica (2 adults per plant), and/or to the fact that, in our experiments, the air entrainments were not conducted contemporarily with the insect attack, i.e., the insects were removed before the capture of volatiles began.…”

“…This monoterpene is not detected in the emission from healthy cabbage and Brussels sprouts but it is emitted by these plants when damaged by Plutella xylostella (Lepidoptera: Plutellidae) (Bukovinszky et al, 2005;Pinto et al, 2007).…”

Chemical cues mediating aphid location by natural enemies

“…It is commonly released in the cornicle secretions of many aphid species (Francis et al, 2005a) to alert surrounding aphids of the presence of natural enemies (Grasswitz & Paine, 1992;Francis et al, 2004Francis et al, , 2005bKunert et al, 2005). However, EBF is a sesquiterpenoid which reacts quickly with ozone (Pinto et al, 2007). Single aphids have peak emissions of < 50 ng (Schwartzberg et al, 2008) and usually only the attacked aphid emits, whereas undisturbed aphids in the vicinity do not (Hatano et al, 2008).…”

Interactions of forests with secondary air pollutants: Some challenges for future research

“…The decreased lifetime of such molecules as ozone concentrations increase implies a shorter dispersion path in the atmosphere and a reduction in the spatial effectiveness of the signalling. Despite the possibility that ozone (and other oxidants) might interfere with atmospheric signalling processes (Vuorinen et al, 2004), there is also limited evidence that less reactive biogenic VOCs may act as signalling molecules, and be relatively unaffected by oxidants (Pinto et al, 2007). Similarly, the effects of ozone on the production of signalling molecules may not require an atmospheric pathway, but may nevertheless have a direct influence on herbivore behaviour (Mondor et al, 2004).…”