Plants Physically React to Leaf Vibrations Caused by Hungry Caterpillars (VIDEO)

Plants may seem defenseless, but they aren't. In fact, researchers have found that plant growth can actually be influenced by sound and that plants can respond to wind and touch. Now, they've found that plants can also respond to the sounds that caterpillars make when eating plants, which causes them to raise their defenses.

In order to examine whether the sound of hungry caterpillars and other insects could cause a plant to respond, the researchers placed caterpillars on Arabidopsis, a small flowering plant. Then by using a laser and a tiny piece of reflective material on the leaf of this plant, the researchers measured the movement of the leaf in response to the chewing caterpillar.

After this, the scientists played back recordings of caterpillar feeding vibrations to one set of plants, but played back only silence to the other set. When caterpillars were later exposed to both sets of plants, the plants that were previously exposed to feeding vibrations actually produced more mustard oils, which is a chemical that's unappealing to many caterpillars.

"What is remarkable is that the plants exposed to different vibrations, including those made by a gentle wind or different insect sounds that share some acoustic features with caterpillar feeding vibrations did not increase their chemical defenses," said Rex Cocroft, one of the researchers, in a news release. "This indicates that the plants are able to distinguish feeding vibrations from other common sources of environmental vibration."

Currently, the scientists plan to focus on how vibrations are actually sensed by the plants and what features of a vibrational signal are important. In addition, they plan to look at how vibrations interact with other forms of plant information to generate protective responses to pests.

"Caterpillars react to this chemical defense by crawling away, so using vibrations to enhance plant defenses could be useful to agriculture," said Heidi Appel, one of the researchers. "This research also opens the window of plant behavior a little wider, showing that plants have many of the same responses to outside influences that animals do, even though the responses look different."

The findings are published in the journal Oecologia.

Want to learn more? Check out the video below, courtesy of University of Missouri and Vimeo.

Plants Respond to Leaf Vibrations Caused by Insects’ Chewing, MU Study Finds from MU News Bureau on Vimeo.