Volatile communication between plants that affects herbivory: a meta‐analysis

Abstract

Volatile communication between plants causing enhanced defence has been controversial. Early studies were not replicated, and influential reviews questioned the validity of the phenomenon. We collected 48 well-replicated studies and found overall support for the hypothesis that resistance increased for individuals with damaged neighbours. Laboratory or greenhouse studies and those conducted on agricultural crops showed stronger induced resistance than field studies on undomesticated species, presumably because other variation had been reduced. A cumulative analysis revealed that early, non-replicated studies were more variable and showed less evidence for communication. Effects of habitat and plant growth form were undetectable. In most cases, the mechanisms of resistance and alternative hypotheses were not considered. There was no indication that some response variables were more likely to produce large effects. These results indicate that plants of diverse taxonomic affinities and ecological conditions become more resistant to herbivores when exposed to volatiles from damaged neighbours.

Root-emitted volatile organic compounds: can they mediate belowground plant-plant interactions?

“…The roles played by VOCs emitted by aboveground plant organs in biotic interactions between neighbouring plants have been extensively reviewed (Dicke and Bruin 2001;Farmer 2001;Heil and Karban 2010;Arimura et al 2010;Holopainen and Blande 2012;Karban et al 2014b). Briefly, the emission of an airborne volatile cue by insect-attacked or mechanically damaged trees changing the leaf chemistry of undamaged neighbours was first hypothesized in 1983 in two independent reports (Baldwin and Schultz 1983;Rhoades 1983).…”

“…Two years later, the controversial debate on 'talking trees' opened with criticisms of the statistical flaws in Baldwin and Schultz's study, as well as the existence of an alternative explanation for Rhoades' results (Fowler and Lawton 1985;Bruin et al 1995). Since 1983, numerous experiments performed under laboratory and field conditions have shown that VOCs emitted by damaged or undamaged aboveground plant parts of monocotyledonous and dicotyledonous plant species play important roles in interactions between neighbouring plants (Heil and Karban 2010;Karban et al 2014b) or between different parts of the same plant (Karban et al 2006;Heil and Silva Bueno 2007;Frost et al 2007;Park et al 2007) (Fig. 2).…”

Can browsing by deer in winter induce defence responses in bilberry (Vaccinium myrtillus)?

“…There are few studies of how plant defence systems function under natural conditions, where variation at both individual plant and ecosystem level may mask the impact of defence responses (Rodriguez-Saona et al 2013;Karban et al 2014). Many ecological studies have experimentally simulated the effects of mammalian herbivory by using clipping treatments and subsequently analysing the effects on plant biomass, nutritional quality and palatability to other herbivores (e.g., Tolvanen et al 1994;Strengbom et al 2003;Pato and Obeso 2013b).…”

A comparison of plants and animals in their responses to risk of consumption

“…Instead, they rely on volatile cues that are emitted at the site of attack to coordinate systemic defenses against further herbivory [27 ]. Volatile cues that likely evolved to coordinate systemic defenses of individuals can also be sensed by neighboring plants [28].…”