Plants can feel vibrations caused by predators chewing leaves, according to a new study from the University of Missouri (MU). Plants respond to touch and wind; their growth can be influenced by sound, including music, previous research determined. 

Researchers placed caterpillars on Arabidopsis plants, which are related to mustard and cabbage. A small reflective surface was placed on the leaf, and a laser pointed at the target. This allowed Appel and her team to measure tiny movements in the plant, made in response to predation. 

"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," Heidi Appel, senior research scientist at MU, told the press. 

Sounds of feeding vibrations were played back to some plants, while a control group was played a recording of silence. Caterpillars were then introduced to both groups, and researchers measured the levels of defensive chemicals. The team found plants in the group exposed to chewing vibrations produced higher levels of mustard oils. Those chemicals are deterrents to the insects. 

"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. This indicates that the plants are able to distinguish feeding vibrations from other common sources of environmental vibration," Rex Cocroft, biology professor at MU stated in a press release. 

The team draws an important distinction between those who talk to their plants and their research. They believe lessons from their study could be employed to better-manage crops, and provide natural defenses for plants from predators. In the future, crops could be designed through natural cross-breeding or genetic engineering with such acoustical warning systems in mind. 

"We're trying to think about the plant's acoustical environment and what it might be listening for, then use those vibrational sounds to figure out what makes a difference," Cocroft said

Appel and Cocroft will followup this finding with research into how plants sense the vibrations, and which elements of the signal are most critical in communication. They will also examine how these signals interact with other defense systems in the plant.

Members of the MU Bond Life sciences Center created a video, highlighting their research and discovery, available on their YouTube page.

Study of the role vibrations play in plant defenses was published in the journal Oecologia.

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