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How much carbon does a plant
absorb and release?
By Girish Bhaskar
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.
Indo-Asian
News Service
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