Previous studies have suggested that plant growth can be influenced by sound and that plants respond to wind and touch. Now, researchers at the University of Missouri, in a collaboration¹ that brings together audio and chemical analysis, have determined² that plants respond to the sounds that caterpillars⁴（毛毛虫） make when eating plants and that the plants respond with more defenses. "Previous research has investigated how plants respond to acoustic⁶ 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. "However, our work is the first example of how plants respond to an ecologically relevant vibration⁷. We found that feeding vibrations⁸ signal changes in the plant cells' metabolism⁹, creating more defensive¹⁰ chemicals that can repel¹¹（击退，抵制） attacks from caterpillars."

 

Appel collaborated¹² with Rex Cocroft, professor in the Division of Biological Sciences at MU. In the study, caterpillars were placed on Arabidopsis, a small flowering plant related to cabbage and mustard. Using a laser and a tiny piece of reflective material on the leaf of the plant, Cocroft was able to measure the movement of the leaf in response to the chewing caterpillar³.

 

Cocroft and Appel then played back recordings¹³ of caterpillar feeding vibrations to one set of plants, but played back only silence to the other set of plants. When caterpillars later fed on both sets of plants, the researchers found that the plants previously¹⁴ exposed to feeding vibrations produced more mustard oils, a chemical that is unappealing（无吸引力的） to many caterpillars.

 

"What is remarkable¹⁵ 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," Cocroft said. "This indicates that the plants are able to distinguish feeding vibrations from other common sources of environmental vibration."

 

Appel and Cocroft say future research will focus on how vibrations are sensed by the plants, what features of the complex vibrational¹⁶ signal are important, and how the mechanical vibrations interact with other forms of plant information to generate protective responses to pests.

 

"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," Cocroft said.

 

"Caterpillars react to this chemical defense⁵ 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."

 

The study was funded in part by the National Science Foundation and was published in Oecologia.

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