The Loh Down On Science

Leafy Listeners

A cabbage butterfly caterpillar feeding on an Arabidopsis plant. Nearby, a piece of reflective tape helps record vibrations.

Roger Meissen

Shhh! The plants are listening!

This is Sandra Tsing Loh with the Loh Down on Science.

We've long known that sounds, like music, can help plants grow.  Now, for the first time, researchers have shown that noise can also make plants respond defensively:  with an increased production of noxious chemicals.

Meet Heidi Appel and Rex Cocroft from the University of Missouri. They've studied plants' responses to what they call ecologically relevant vibrations, i.e., predators feeding.

To see how plants hear, the duo placed caterpillars on leaves and recorded the sound vibrations of the caterpillars eating.  Then they played back the recordings to one set of plants while another set heard only the sound of silence.

What happened when insects later fed on both sets of plants?  The ones that had heard the earlier feeding produced more mustard oil, a defensive chemical.

Vibrations made by wind or insects' songs, on the other hand, had no such effect.  Thus, plants seem to be able to tell the difference between predation and less-threatening vibrations.

Talk about a telephone tree!  Or at least, plant.


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