When an insect chews on a leaf, it might not kill the plant, but that doesn't mean the plant is fine with it. In fact, the plant can deploy a variety of defenses to drive off the munching critter. But how do plants "know" they are being eaten? A new study has some intriguing answers.

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Researchers at the University of Missouri conducted experiments on thale cress—a plant closely related to broccoli, kale, mustard greens, and cabbage, though unlike most of its cousins, it isn't very good to eat. But, as the first plant to have its genome sequenced, it's long been a favorite test subject among scientists, who know quite a bit about its inner workings.

As Modern Farmer reports:

The researchers had to first make a precise audio version of the vibrations that a caterpillar makes as it eats leaves. The theory is that it's these vibrations that the plant can somehow feel or hear. In addition, the researchers also came up with vibrations to mimic other natural vibrations the plant might experience, like wind noise.

Turns out, the thale cress actually produces some mustard oils and sends them through the leaves to deter predators (the oils are mildly toxic when ingested). And the study showed that when the plants felt or heard the caterpillar-munching vibrations, they sent out extra mustard oils into the leaves. When they felt or heard other vibrations? Nothing. It's a far more dynamic defense than scientists had realized: the plant is more aware of its surroundings and able to respond than expected.

There's more research to be done; nobody's quite sure by what mechanism the plant can actually feel or hear these vibrations, and with so many plants out there, we're not sure what kind of variation on this behavior there is. But it's really promising research; there's even talk of using sound waves to encourage crops to, say, grow faster, or send out specific defenses against attacks. Imagine knowing that a frost is coming, and being able to encourage plants to fruit faster by simply blasting them with music. That's the kind of crazy sci-fi future this indicates.

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