Bad vibrations: Plants respond to leaf vibrations caused by insect herbivore chewing

It has been known for decades that plants respond to sound and vibration, but the ecological significance of these responses is unclear. One source of acoustic energy with particular relevance to plant fitness is the activity of insect herbivores. Here we report that the vibrations caused by insect feeding can elicit chemical defenses. Arabidopsis thaliana (L.) rosettes pre-treated with the vibrations caused by caterpillar feeding had higher levels of glucosinolate and phenolic defenses when subsequently attacked by attacked by Pieris rapae (L.) caterpillars than did untreated plants and plants treated with the vibrations caused by wind or other insect sounds. These results demonstrate that plants can respond to herbivore-generated vibrations in an ecologically meaningful way. Although the way in which plants perceive mechanical vibrations is not well understood, a vibration signaling pathway would complement the known signaling pathways that rely on airborne volatiles or phloem-borne signals. We suggest that vibration represents a new long distance signaling mechanism in plants responsible for systemic induction of chemical defenses.