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Could Tannins Help Fight Global Warming?
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July 29, 2005--Tannins color tea, stain your teeth, and make some woodland rivers run a rich, deep brown in the spring. Researchers at Michigan Tech suspect that one type of these plant-based substances, known as condensed tannins, could also play a role in buffering the greenhouse effect.
Increasing carbon dioxide in the atmosphere has been fingered as a cause of global warming. Since trees take up carbon dioxide, forests have been touted as potential carbon sinks, scrubbing CO2 from the air.
Unfortunately, most carbon that trees take in goes right back into the air when they decompose. A special gift of condensed tannins, according to Scott Harding, a research assistant professor in the School of Forest Resources and Environmental Science, is their ability to slow down that decomposition. Thus, trees hang onto their carbon long after they die.
With the help of a three-year, $1.4 million grant from the U.S. Department of Energy, Harding hopes to better understand how condensed tannins accumulate in black cottonwood, or Populus trichocarpa, and other closely related species.
The study is only possible because last year the black cottonwood became the first tree to have its genome mapped. Associate Professor Chung-Jui Tsai (SFRES) is a co-principal investigator on the DOE project and led the MTU researchers who joined teams throughout the U.S. and Canada in sequencing the genome.
Now that the black cottonwood's genetic code has been deciphered, Harding and his team can mine its mysteries in hopes of discovering the secrets of condensed tannin synthesis.
"We'll look at naturally occurring hybrids of cottonwood to study the process of condensed tannin accumulation, with the goal of finding out ways of fixing more carbon," Harding said.
Condensed tannins are stored throughout trees in varying quantities, and can make up anywhere from zero to 35 percent of the dry weight of leaves.
The researchers will propagate several naturally occurring cottonwood hybrids with varying amounts of condensed tannin to find out which genes control the amount of tannins in the tree and where they are stored.
They'll also mimic the tough times trees have in the wild by subjecting some trees to conditions such as drought and injury. "This will help us understand how trees manage their carbon budget under stress," Tsai said.
Once scientists have a better understanding of how trees create and store condensed tannins, they may be able to grow trees that not only take carbon out of the air, but also keep it stored safely on earth for a long time to come. |
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