Induced plant defences: from molecular biology to evolutionary ecology

Phenotypic plasticity enables invididuals to change their phenotype in response to their environment. These phenotypic changes can affect many interactions between the members of a community. Plants are able to respond towards herbivore attack by defensive mechanisms directly affecting the herbivore and by so-called indirect defences that negatively affect the herbivore by maintenance or attraction of carnivores. The phenotypic changes of plants caused by induced defences may vary with the type of attackers. Different attackers can evoke different plant responses due to specific elicitors or wounding. These different plant responses may be mediated by different choreographies of gene expression. Symbiotic and pathogenic microorganisms associated with the plant or the herbivore may play an important role in the induction process. Thus, a plethora of biotic factors affect the physiological, chemical, and molecular characteristics of plants in response to attack. The adaptiveness of phenotypic plasticity in terms of induced responses depends on the balance of their physiological and ecological costs and benefits. An integrated approach is necessary considering ecological, molecular and chemical aspects to gain deeper insight into induced defence and its application in environmentally benign crop protection.