A chemical analysis suggested plants defend themselves more vigorously based on the sounds caterpillars make while eating them.
The recent study, published in the journal Oecologia, measured the movement of a leaf in response to a recording of a chewing caterpillar using a laser and a reflective material aimed at the plant, the University of Missouri-Columbia reported. The team found the plant releases a chemical defense in response to the vibrations.
"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 University of Missouri. "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 from caterpillars."
When caterpillars did feed on the leaves the team found those that had previously been exposed to the munching sounds contained more mustard oils, which is unappealing to certain types of 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," Rex Cocroft, professor in the Division of Biological Sciences at MU said. "This indicates that the plants are able to distinguish feeding vibrations from other common sources of environmental vibration."
In the future the researchers hope to look into how the plants sense these vibrations and what features of the vibrational signal are important in the plant's response to the pest.
"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."
