Plants can summon help with chemical 'SOS'

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AMSTERDAM, Netherlands, Aug. 27 (UPI) -- Plants can send out a chemical "mayday" distress signals to summon insects to save them from being consumed by caterpillars, Dutch and German researchers say.

In an article in the journal Science, researchers from the Netherlands and Germany say the caterpillars' saliva activates this signal, which attracts predatory insects that feed on caterpillar larva and eggs, rescuing the plant and gaining a meal, the BBC reported Friday.

When leafy tobacco plants were attacked by tobacco hornworm caterpillars, the caterpillar saliva caused a chemical change in "green leaf volatiles," pungent chemicals that the plants produce, the researchers said.

Such green leaf volatiles are responsible for the familiar smell of cut grass.

The modified "chemical SOS" seems to "betray the location of the feeding caterpillar," the scientists said.