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Caterpillar Saliva Triggers Plant's Chemical Alarms

When a tobacco hornworm chews on a tobacco leaf, the leaf releases a chemical alarm into the air. A big-eyed bug senses the signal and flies to the leaf to feed on the hornworm's eggs.

Chemical Exchange in Plants

During the day, the sun shines on leaves, triggering guard cells to open. Guard cells allow CO2 to enter the leaf, fueling photosynthesis. While guard cells are open, 90% of the water taken up by a plant is lost. At night, guard cells close to conserve water.

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