Scientists have known that sound waves can have an effect on things like germination and growth, but University of Missouri researchers Rex Cocroft and Heidi Appel wanted to figure out whether plants could also sense the vibrations that insects produced when munching on them. Using a vibration microphone equipped with laser sensors, Cocroft recorded the sounds of caterpillars chowing down on the delicious leaves of Arabidopsis thaliana, a small flowering plant related to cabbage and mustard. They chose that plant for the fact that it produces mustard oil in its leaves. "A caterpillar that eats nothing but mustard oil plants can get poisoned if the levels get too high," Appel told Farm Journal.
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When they played the sounds of caterpillar chomps for Arabidopsis, the plants sent out extra mustard oils into their leaves. Not so with other sounds like wind or insect song (which, to a plant, we assume sounds like a velociraptor). "This indicates that the plants are able to distinguish feeding vibrations from other common sources of environmental vibration," Cocroft said in a press release. The plants that heard the vicious caterpillar attack also produced more anthocyanins, the chemical that gives flowers their red color.
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