XVI International Botanical Congess

Hypersensitive reaction (HR) is an important type of induced defense by which the plant elicits a defense response to pathogens and insects. This pioneer study provides the first data on how widespread and important is HR against gall-inducing insects. HR was common independently of plant phylogeny and growth form, and the most important mortality factor against gall formation across host plant taxa. Effects driven by the host plant (HR) strongly influenced herbivore populations in the absence of other factors. The number of galls was influenced by the size of the host plant module attacked, while HR was frequent in all sizes of leaves across plant taxa. Therefore, no significant relationship was found between plant module size (vigor) and HR induction, indicating that this mechanism of plant resistance may be more influenced by genetic factors. We argue that hypersensitivity may lack documentation for reasons other than the scarcity of its occurrence in nature.