© 2007 Heron Publishing—Victoria, Canada
Volatile organic compound emission from holm oak infested by gypsy moth larvae: evidence for distinct responses in damaged
and undamaged leaves
Michael Staudt (1, 2) and Louise Lhoutellier (1)
1. Department of Ecosystem Functioning, Centre for Evolutionary and Functional Ecology (UMR 5175), 1919 Route de Mende, 34293
Montpellier cedex 5, France / 2. Corresponding author (michael.staudt@cefe.cnrs.fr) / Received November 16, 2007; accepted January 30, 2007; published online July 3, 2007
Summary
Foliage of Quercus ilex L. (holm oak), a widespread Mediterranean species, constitutively emits large quantities of a complex genotype-dependent
mixture of volatile organic compounds (VOCs). During a mass outbreak of gypsy moth (Lymantria dispar L.) in southern France, we examined the effects of gypsy moth feeding on VOC production from whole apices and single leaves
of Q. ilex. Feeding induced the emission of new VOCs at rates up to 240 ng m–2 s–1 (16% of the total VOC release), which mainly consisted of sesquiterpenes, a homoterpene and a monoterpene alcohol. The new
compounds were emitted after a delay of several hours following infestation and their production declined rapidly when caterpillars
were removed. Undamaged leaves of infested trees emitted new VOCs, but with a different composition to those of damaged leaves
and at lower rates. Neither caterpillars nor caterpillar excrement released VOCs. Emission of constitutive VOCs by undamaged
leaves of infested trees temporary increased by up to 30%, whereas, in damaged leaves, they remained stable and decreased
after some days when necrotic spots occurred around the feeding sites. In continuous light and at constant temperature, emissions
of new VOCs showed a marked diurnal cycle, whereas those of constitutive VOCs did not. The results suggest that induced VOCs
make a significant contribution to the atmospheric VOC load and may mediate trophic interactions. The observed differential
local and systemic responses in composition, quantity and time courses of emissions mirror the existence of several regulation
processes triggered by different signaling compounds and elicitors.
Keywords:
biogenic volatile organic compounds, biosphere atmosphere interactions, herbivores, homoterpene, Lymantria dispar, monoterpene, plant defense, Quercus ilex, sesquiterpene, wounding.
