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Abstract

The specificity of woody plant defense responses to different attacking herbivores is poorly known. We investigated the
responses of black poplar (Populus nigra) to leaf feeding by three lepidopteran species (Lymantria dispar, Laothoe populi and
Amata mogadorensis) and two leaf beetle species (Phratora vulgatissima and Chrysomela populi). Of the direct defenses
monitored, increases in trypsin protease inhibitor activity and the salicinoid salicin were triggered by herbivore damage, but this
was not herbivore-specific. Moreover, the majority of leaf salicinoid content was present constitutively and not induced by
herbivory. On the other hand, volatile emission profiles did vary among herbivore species, especially between coleopterans and
lepidopterans. Monoterpenes and sesquiterpenes were induced in damaged and adjacent undamaged leaves, while the emission
of green leaf volatiles, aromatic and nitrogen-containing compounds (known to attract herbivore enemies) was restricted to
damaged leaves. In conclusion, indirect defenses appear to show more specific responses to attacking herbivores than direct defenses in this woody plant.