Stressed plants release aspirin-like chemical

WASHINGTON (Reuters) - Plants stressed by drought or unseasonable temperatures squirt out an aspirin-like chemical, researchers reported on Thursday in a finding that may some day help farmers watch for trouble.

The chemical, methyl salicylate, may help plants resist the damage and may help them signal danger to one another, the team at the National Center for Atmospheric Research in Colorado said.

"Unlike humans, who are advised to take aspirin as a fever suppressant, plants have the ability to produce their own mix of aspirin-like chemicals, triggering the formation of proteins that boost their biochemical defenses and reduce injury," Thomas Karl, who led the study, said in a statement.

"Our measurements show that significant amounts of the chemical can be detected in the atmosphere as plants respond to drought, unseasonable temperatures, or other stresses."

Acetylsalicylic acid, or aspirin, was originally derived from tree bark, so scientists knew it was a compound made by plants. But it was never seen to be emitted as a gas.

Writing in the journal Biogeosciences, the researchers said they accidentally found the chemical when they set up instruments last year in a California walnut grove to monitor plant emissions of volatile organic compounds.

Such compounds can combine with industrial emissions to affect pollution and they can influence local climate.

The trees were already stressed by drought, and levels of methyl salicylate rose with unseasonably cool night-time temperatures -- especially when it quickly warmed up the next day.

Plants are known to emit chemicals to signal one another when they are close together, for instance, when being chomped on by insects.

"These findings show tangible proof that plant-to-plant communication occurs on the ecosystem level," scientist Alex Guenther said. "It appears that plants have the ability to communicate through the atmosphere."

Farmers and forest managers may be able to monitor for methyl salicylate to watch for early signs of disease, insect infestation, or other types of stress long before leaves begin to wither and drop off.

"If you have a sensitive warning signal that you can measure in the air, you can take action much sooner, such as applying pesticides. The earlier you detect that something's going on, the more you can benefit in terms of using fewer pesticides and managing crops better," Karl said.

(Reporting by Maggie Fox, editing by Will Dunham)