While prior research has suggested that sound can influence plant growth and that "plants respond to wind and touch," a new study asserts that plants respond defensively when they detect leaf-chewing predators, according to a news release.

The findings were published in the journal Oecologia, and the study was funded in part by the National Science Foundation and based on experiments conducted by a team from the University of Missouri.

In the study, researchers placed caterpillars on arabidopsis, "a small flowering plant related to cabbage and mustard," and used a laser and a small "piece of reflective material on the leaf of the plant" to measure how much the leaf moved in response to caterpillar chewing.

The researchers afterward played back audio recordings of caterpillar feeding vibrations to one set of plants and only silence to a second set of plants.

"When caterpillars later fed on both sets of plants, ... the plants previously exposed to feeding vibrations produced more mustard oils," which most caterpillars find unappealing.

"Previous research has investigated how plants respond to acoustic energy, including music," Heidi Appel, the senior research scientist in the university's plant sciences division in the College of Agriculture, Food and Natural Resources and the Bond Life Sciences Center, said in the release. "However, our work is the first example of how plants respond to an ecologically relevant vibration. We found that feeding vibrations signal changes in the plant cells' metabolism, creating more defensive chemicals that can repel attacks."

Remarkably, "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 university biology professor Rex Cocroft. "This indicates that the plants are able to distinguish feeding vibrations from other common sources of environmental vibration. ... Plants have many ways to detect insect attack, but feeding vibrations are likely the fastest way for distant parts of the plant to perceive the attack and begin to increase their defenses."

Meanwhile, "caterpillars react to this chemical defense by crawling away, so using vibrations to enhance plant defenses could be useful to agriculture," Appel said. "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."

Appel and Cocroft said their future research will focus on how plants sense vibrations and what factors cause plants to react differently to vibration sources.