During their lifetimes, plants generally give off
about half of the carbon dioxide (CO2),
that they absorb, although this varies a great
deal between different kinds of plants. Once they
die, almost all of the carbon that they stored up
in their bodies is released again into the
As you may know, plants use the
energy in sunlight to convert CO2 (from
the air) and water (from the soil) into sugars.
This is called photosynthesis.Plants use some of
these sugars as food to stay alive, and some of
them to build new stems and leaves so they can
grow. When plants burn their sugars for food,
CO2 is produced as a waste product,
just like the CO2 that we exhale is a
waste product from the food we burn for energy.
This happens day and night, but since
photosynthesis is powered by sunlight, plants
absorb much more CO2 than they give off
during the daytime. At night, when photosynthesis
is not happening, they give off much more
CO2 than they absorb. While they're
alive, overall, about half of the CO2
that plants absorb is given off as waste.
you look at a tree, almost all of the body of the
tree is made of sugars, which are made from carbon
(from CO2) and hydrogen and oxygen
(from water). When the tree dies, it rots as
decomposers, like bacteria, fungi,and insects eat
away at it. Those decomposers gradually release
almost all of the tree's stored carbon back into
the atmosphere as CO2. Only a very
small portion of the carbon in the tree ends up
staying in the soil or washing out to sea without
changing back into CO2.
Note ScienceLine Moderator:
Correction made by Jeff, Appalachian State University.
Actually, the oxygen from water is split off to
form O2 gas, and only the hydrogen ends
up in the sugar. That seems important.
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