Chemical model for short-term induction in quaking aspen (Populus tremuloides) foliage against herbivores

Simulated large aspen tortrix (Choristoneura conflictana) herbivory of quaking aspen (Populus tremuloides) induces significant increases in concentrations of two phenol glycosides, salicortin and tremulacin, in leaves within 24 hr. Crushing of leaf tissue, as must occur when aspen leaves are eaten by chewing insects such as the large aspen tortrix, results in conversion of salicortin and tremulacin to 6-hydroxy-2-cyclohexenone (6-HCH). Salicortin, tremulacin, 6-HCH, and its degradation product, catechol, are all toxic to the large aspen tortrix when fed on an artificial diet. These damage-induced chemical changes provide a plausible mechanism for short-term resistance induced in aspen leaves by insect herbivory.