How much carbon does a plant absorb and release?

November 14th, 2008 - 5:22 pm ICT by IANS  

Washington, Nov 14 (IANS) Scientists are on the verge of overcoming a major hurdle in calculating how much carbon is absorbed and released by plants. The information could be vital for understanding how the biosphere responds to stress and in determining the amount of carbon that can be safely emitted by human activities. The problem is that ecosystems simultaneously absorb and release carbon dioxide (CO2). The key finding is that the compound carbonyl sulfide, which plants consume in tandem with CO2, can be used to quantify gas flow into the plants during photosynthesis.

“In photosynthesis, plants breathe in CO2 from the air and with solar energy, convert it and water into food and oxygen, which they then ‘exhale’,” explained co-author of a new study Joe Berry, from the Carnegie Institution’s Department of Global Ecology.

“In ecosystems, plants and other organisms respire producing carbon dioxide. We can measure the net change in CO2, but we do not have an accurate way to measure how much is going in or out and how this is affected by climate.

“Understanding this photosynthesis-climate feedback riddle is key to understanding how climate change may affect the natural processes that are a sink for human-made carbon emissions.”

Previous laboratory research showed that carbonyl sulfide is taken up in step with photosynthesis. But unlike CO2, there is no emission of carbonyl sulfide from plants, acording to a Carnegie release.

The researchers compared atmospheric measurements of carbonyl sulfide over North America during the growing season with two simulations of an atmospheric transport model. The airborne observations, from the Intercontinental Chemical Transport Experiment - North America, also measured CO2. They combined that data with results from laboratory experiments that looked at gas exchange at the leaf level.

“The intriguing outcome of this study is that an inverse analysis of the atmospheric carbonyl sulfide measurements may be used to quantify the carbon released during plant respiration,” remarked Berry. “That key missing piece has been a thorn in the side of carbon-cycle research for years.”

The research was published in Science Friday.

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