The smell of freshly-cut grass is actually a plant distress call

March 30, 201214 yr

The lovely scent of cut grass is the reek of plant anguish: When attacked, plants release airborne chemical compounds. Now scientists say plants can use these compounds almost like language, notifying nearby creatures who can "rescue" them from insect attacks.

A group of German scientists studying a wild tobacco plant noticed that the compounds it released - called green leaf volatiles or GLVs - were very specific. When the plants were infested by caterpillars, the plants released a distress GLV that attracted predatory bugs who like to eat the caterpillars in question.

According to Science, where the researchers published their study today:

They found that when these plants are attacked by tobacco hornworm caterpillars,

Manduca sexta

, the caterpillars' saliva causes a chemical change in the GLV compounds the plants had produced. These modified compounds then attract predatory "true bugs,"

Geocoris

, which prey on hornworm eggs and young larvae. Although more research will be needed to figure out exactly how the molecules in the caterpillar saliva cause this change in the GLVs, it's clear that the caterpillars themselves cause the change in the GLV signal, the researchers say. It may thus be possible someday to induce the same sort of change via genetic engineering, which might protect plants against pests without encouraging the resistance that pests develop in response to pesticides.

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