Strange News: Plants Know When They're Being Eaten

Bad news, vegetarians: A new study conducted by the University of Missouri has found that plants do indeed have feelings. And based on their physical responses to an attack, they can tell when they're being eaten, too.

"Previous research has investigated how plants respond to acoustic energy, including music," said Heidi Appel, senior research scientist in the Division of Plant Sciences in the College of Agriculture, Food and Natural Resources and the Bond Life Sciences Center at MU.

This new study, however, focused on a different type of vibration: the vibration that a caterpillar creates while munching on leaves. But would a plant be able to differentiate the vibrations of a hungry caterpillar versus, say, the vibrations of a passing breeze?

The scientists set out to answer that very question with a plant called Arabidopsis, or thale cress. As a member of the Brassicaceae family, thale cress is a small flowering plant closely related to cabbage and kale. It's common in experiments pertaining to plant biology because it's the first plant to have its entire genome sequenced. But is it capable of feeling or even hearing what's going on around it?

MU scientists created audio recordings that mimicked the vibrations made by a caterpillar when it eats, and vibrations that a plant might experience day to day, such as wind noise. They exposed the thale cress to the different recordings, as well as to live caterpillars snacking on the leaves and also to silence.

They found that ordinarily, the plant produces mustard oils and sends them through its leaves to deter predators. When it felt or heard the vibrations of caterpillars, it produced extra mustard oils, which are toxic to insects when ingested in large amounts. But when it felt or heard other vibrations? Nothing. Scientists realized that the plant's defense mechanisms were more intuitive than previously thought, as the plant was quite aware of its surroundings and responded accordingly.

Based on these initial findings, the group is hopeful other scientists will take the sound and vibration research and apply it in agriculture.

"Could sound be played out to plants in a field causing them to respond in a beneficial way? Sure, it's very speculative, but it's also something that could happen in the future," said Rex Cocroft, a professor of biological sciences at MU who also worked on the study.