Stressed forest plants emit their own form of aspirin

Posted by Laura Grant on September 19, 2008
Posted in Green News

Plants in a forest respond to stress by producing a chemical form of aspirin, scientists at the National Center for Atmospheric Research (NCAR) in the United States have discovered.

The plants were found to emit the chemical methyl salicylate, which is a form of acetylsalicylic acid, or aspirin, into the atmosphere in significant quantities in response to drought, unseasonable temperatures, or other stresses.

NCAR scientist Thomas Karl, who led the study, and his colleagues speculate that the methyl salicylate has two functions. One is to stimulate something analogous to an immune response to help the plants both resist and recover from disease.

The other may be a way for a stressed plant to communicate to neighbouring plants, warning them of the threat.

The NCAR team has demonstrated that methyl salicylate can build up in the atmosphere above a stressed forest and scientists are speculating that plants may use the chemical to activate an ecosystem-wide immune response.

“These findings show tangible proof that plant-to-plant communication occurs on the ecosystem level,” says NCAR scientist Alex Guenther, a co-author of the study. “It appears that plants have the ability to communicate through the atmosphere.”

The NCAR team found the chemical by accident after they set up specialised instruments last year in a walnut grove near Davis, California, to monitor plant emissions of certain volatile organic compounds (VOCs).

They found to their surprise that the emissions of VOCs included methyl salicylate and that the levels of methyl salicylate emissions increased dramatically when the plants, which were already stressed by a local drought, experienced unseasonably cool night-time temperatures followed by large daytime temperature increases.

The discovery raises the possibility that farmers, forest managers, and others may eventually be able to start monitoring plants for early signs of a disease, an insect infestation, or other types of stress, say the researchers. At present, they often do not know if an ecosystem is unhealthy until there are visible indicators, such as dead leaves.

The team of scientists reported its findings last week in the journal Biogeosciences.

Caption: NCAR scientists used specially equipped towers to measure plant emissions above the forest canopy of a walnut grove. (Photo by Carlye Calvin, ©UCAR.)

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