A Volatile Response to Injury

Abstract

Plants defend themselves against herbivores by releasing volatile organic compounds (VOCs) that repel herbivores or attract herbivore predators. This response to herbivore-induced damage is mediated through jasmonic acid (JA). Herbivore-induced VOCs have also been reported to stimulate defenses in neighboring plants, thereby playing a role in plant-plant communication (see Gershenzon). Heil and Bueno found that regions of field-grown lima bean plants exposed to shoots that had been damaged by leaf beetles grew better, showed less herbivore damage, secreted more extrafloral nectar (EFN, which attracts herbivore predators), and attracted more ants than did regions that were unexposed to damaged shoots. When some leaves of field-grown lima bean plants were stimulated through damage and application of JA to produce VOCs, production of EFN was stimulated in nearby undamaged leaves from the same shoot or from a second shoot of the same plant. Enhanced production of EFN in undamaged leaves was inhibited, however, when the damaged leaves were covered with plastic bags. Exposure to VOCs also primed EFN secretion, so that the response to subsequent damage was greater in leaves previously exposed to VOCs. In experiments on potted plants, in which air from damaged leaves was blown toward undamaged leaves or directed away from them, only undamaged leaves exposed to air from damaged leaves responded with increased production of EFN. Thus, VOCs appear not only to function in plant-plant communication but also to act as an intraplant defense signal. M. Heil, J. C. Silva Bueno, Within-plant signaling by volatiles leads to induction and priming of an indirect plant defense in nature. Proc. Natl. Acad. Sci. U.S.A. 104 , 5467-5472 (2007). [Abstract] [Full Text] J. Gershenzon, Plant volatiles carry both public and private messages. Proc. Natl. Acad. Sci. U.S.A. 104 , 5257-5258 (2007). [Full Text]