Not only do microbes eat up methane and other oil wastes faster than expected, it now seems that vegetation eats up air pollution to a much greater degree than thought. A new paper in Science finds that oxygenated volatile organic compounds (oVOCs) are taken up by deciduous plants at an unexpectedly fast rate–as much as four times more rapidly than previously thought.
T. Karl, P. Harley, L. Emmons, B. Thornton, A. Guenther, C. Basu, A. Turnipseed, K. Jardine. Efficient Atmospheric Cleansing of Oxidized Organic Trace Gases by Vegetation. Science, 2010; DOI: 10.1126/science.1192534
From Eurekalert:
“Plants clean our air to a greater extent than we had realized,” says NCAR scientist Thomas Karl, the lead author. “They actively consume certain types of air pollution.”
The research team focused on a class of chemicals known as oxygenated volatile organic compounds (oVOCs), which can have long-term impacts on the environment and human health. “The team has made significant progress in understanding the complex interactions between plants and the atmosphere,” says Anne-Marie Schmoltner of NSF’s Division of Atmospheric and Geospace Sciences, which funded the research. The compounds form in abundance in the atmosphere from hydrocarbons and other chemicals that are emitted from both natural sources–including plants–and sources related to human activities, including vehicles and construction materials.
The compounds help shape atmospheric chemistry and influence climate.
Eventually, some oVOCs evolve into tiny airborne particles, known as aerosols, that have important effects on both clouds and human health.
By measuring oVOC levels in a number of ecosystems in the United States and other countries, the researchers determined that deciduous plants appear to be taking up the compounds at an unexpectedly fast rate–as much as four times more rapidly than previously thought.
The uptake was especially rapid in dense forests and most evident near the tops of forest canopies, which accounted for as much as 97 percent of the oVOC uptake that was observed. Karl and his colleagues then tackled a follow-up question: How do plants absorb such large quantities of these chemicals?
The scientists moved their research into their laboratories and focused on poplar trees. The species offered a significant advantage in that its genome has been sequenced. The team found that when the study trees were under stress, either because of a physical wound or because of exposure to an irritant such as ozone pollution, they began sharply increasing their uptake of oVOCs. At the same time, changes took place in expression levels of certain genes that indicated heightened metabolic activity in the poplars.
The uptake of oVOCs, the scientists concluded, appeared to be part of a larger metabolic cycle. Plants can produce chemicals to protect themselves from irritants and repel invaders such as insects, much as a human body may increase its production of white blood cells in reaction to an infection.
But these chemicals, if produced in enough quantity, can become toxic to the plant itself.
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