Herbivoreinduced

Herbivore-induced (often written as herbivoreinduced in some texts) describes plant responses triggered by herbivore attack, encompassing changes in chemistry, physiology, and interactions with other organisms. The term is used to refer to inducible defenses that are activated specifically in response to herbivory, as opposed to constitutive defenses that are always present.

Plants detect herbivory through recognition of compounds in herbivore saliva and damaged tissue, called herbivore-associated molecular patterns and damage-associated molecular patterns, which initiate signaling cascades. The central pathway often involves jasmonic acid signaling, with modulation by ethylene and, in some cases, cross-talk with salicylic acid pathways. These signals lead to transcriptional reprogramming and the production of defensive compounds.

Induced responses include direct defenses such as protease inhibitors, toxic or anti-nutritional metabolites (alkaloids, phenolics), and structural changes like lignification to deter feeding or reduce digestibility, along with shifts in resource allocation. Plants also release volatile organic compounds that attract predators and parasitoids of the attacking herbivores and can prime neighboring plants to respond more quickly to subsequent attacks.

Responses can be localized at the feeding site or systemic throughout the plant, and can occur rapidly—within hours to days—and may persist for varying durations. Ecologically, herbivore-induced defenses shape plant–herbivore and tri-trophic interactions, and they involve trade-offs between growth and defense, with effectiveness dependent on plant species, herbivore identity, and ecological context.

In agriculture, understanding herbivore-induced responses informs pest management and breeding for resistance, while acknowledging potential costs and ecosystem-level effects to avoid unintended consequences.