Impact of constitutive plant natural products on herbivores and pathogensThe present review is one in the special series of reviews on animal–plant interactions.

Plants defend themselves from pests with deterrent or toxic phytochemicals. In addition to the development of preformed mechanical barriers such as cutin and suberin, the first line of defense for plants against pathogens and herbivores is constitutive (preformed) biologically active inhibitors. Because of the adaptation of insects and pathogens to these inhibitors, plants have evolved a stunning diversity of new and different bioactive molecules to combat pests. Some representative mechanisms of plant defense include the use of antimicrobial, anitfeedant, and phototoxic molecules. Examples of natural product defenses of specific plant families are also described. Diversity and redundancy in plant defenses is key to slowing pest resistance to host-plant defenses.