Abstract
BackgroundThe role of herbivore-induced plant volatiles as signals mediating the attraction of herbivore enemies is a well-known phenomenon. Studies with short-lived herbaceous plant species have shown that various biotic and abiotic factors can strongly affect the quantity, composition and timing of volatile emission dynamics. However, there is little knowledge on how these factors influence the volatile emission of long-lived woody perennials.The aim of this study was to investigate the temporal dynamics of herbivore-induced volatile emission of black poplar (Populus nigra) through several day-night cycles following the onset of herbivory. We also determined the influence of different herbivore species, caterpillars of the gypsy moth (Lymantria dispar) and poplar hawkmoth (Laothoe populi), and different herbivore developmental stages on emission.ResultsThe emission dynamics of major groups of volatile compounds differed strikingly in response to the timing of herbivory and the day-night cycle. The emission of aldoximes, salicyl aldehyde, and to a lesser extent, green leaf volatiles began shortly after herbivore attack and ceased quickly after herbivore removal, irrespective of the day-night cycle. However, the emission of most terpenes showed a more delayed reaction to the start and end of herbivory, and emission was significantly greater during the day compared to the night. The identity of the caterpillar species caused only slight changes in emission, but variation in developmental stage had a strong impact on volatile emission with early instar L. dispar inducing more nitrogenous volatiles and terpenoids than late instar caterpillars of the same species.ConclusionsThe results indicate that only a few of the many herbivore-induced black poplar volatiles are released in tight correlation with the timing of herbivory. These may represent the most reliable cues for herbivore enemies and, interestingly, have been shown in a recent study to be the best attractants for an herbivore enemy that parasitizes gypsy moth larvae feeding on black poplar.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0304-5) contains supplementary material, which is available to authorized users.
Highlights
The role of herbivore-induced plant volatiles as signals mediating the attraction of herbivore enemies is a well-known phenomenon
Volatile emission patterns change during the course of herbivory with variation in how soon compounds are emitted after the start of herbivory [8,9,10,11,12], how soon emission decreases after herbivory stops [9,10,13] and changes in day and night cycles [14]
Temporal dynamics of volatile emission in black poplar after gypsy moth herbivory To investigate the diurnal patterns of black poplar (Populus nigra) volatile emission, we selected 20 compounds as representatives of each of the major classes of volatiles found in this species: green leaf volatiles (GLVs), monoterpenes, homoterpenes, sesquiterpenes, nitrogen-containing compounds and aromatic compounds
Summary
The role of herbivore-induced plant volatiles as signals mediating the attraction of herbivore enemies is a well-known phenomenon. The aim of this study was to investigate the temporal dynamics of herbivore-induced volatile emission of black poplar (Populus nigra) through several day-night cycles following the onset of herbivory. Herbivore-induced plant volatiles are well known to attract predators and parasitoids of herbivores and so have been frequently termed a “cry for help” from the plant to reduce herbivore pressure [2,3,4]. It is still unclear if herbivore enemy recruitment has a real fitness benefit for the plant or if plant volatiles are reliable cues for natural enemies of herbivores [5,6,7]. Much less is known about compounds emitted in lower amounts, such as aromatic compounds and amino acid derivatives (nitrogen and sulfur containing compounds) [2,4,15,16], there is evidence that such minor compounds could have a high ecological value for both herbivores and their natural enemies [17,18,19,20]
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