|Why do plants give off so much carbon dioxide?
|Question Date: 2015-06-04|
Plants actually don't give off carbon dioxide,
they emit oxygen instead. It is due to the way
their metabolism occurs. Plants take in carbon
dioxide from the air, and turn it into sugars
using energy from the sun and water. Plants build
themselves out of carbon dioxide from the air.
When a tree grows, it isn't formed from the soil.
When we (humans) burn trees, we release this
carbon dioxide back into the air. Our metabolism
is in some ways the opposite of plants. We consume
their sugar stores, combine it with oxygen, and
break them back down into carbon dioxide, and
release that into the air.
In the dark, plants breathe oxygen and give off
carbon dioxide just like we do.
Plants absorb the air and water from their
surroundings and use the carbon (from carbon
dioxide) and hydrogen (from water) to build their
cell walls (carbohydrates). They release the
excess oxygen back into the air. Animals, like us,
reverse this process. We breathe in oxygen and use
it to break down the carbohydrates we eat,
releasing carbon dioxide.
What you may be thinking about is the
combustion of plants, which releases carbon
dioxide. When burned, carbohydrates react
directly with the oxygen in the air to create
carbon dioxide and water. Many industrial
processes involve burning plant matter (oil, coal,
gas, wood, etc.) which produces and releases lots
of carbon dioxide into the air. By contrast, very
few processes (except plant growth) consume carbon
dioxide to offset the increased in carbon dioxide
that we produce.
In general, plants don't give off carbon
dioxide unless they are burned. The natural
respiration of plants actually pulls carbon
dioxide out of the air. Using the energy from
sunlight, the plants turn the carbon dioxide into
sugars and starches, which are stored in the
plant's roots, stems, and leaves.
When the plant dies, some carbon dioxide may be
released as it decomposes. If a plant is burned,
for example like firewood or biomass, it releases
a lot of carbon dioxide in the process. If animals
eat the plant, the animals will break down the
sugars and starches for energy and they exhale the
carbon dioxide that is produced by this
Plants give off Carbon Dioxide for the same
reason that we humans breathe out Carbon Dioxide
every day. CO2 is a waste product
from a metabolic reaction called cell
respiration. Basically, almost all organisms
gain energy to do things by breaking down sugar in
their bodies. You and I eat a candy bar, gain
energy from the breaking down of the sugar and
exhale CO2. Plants use sunlight to
convert light energy (attaching that energy to
CO2) into chemical energy (sugar) and
then break down the sugar to grow and survive.
Plants are always exhaling CO2, but
during the day they take in more CO2
than they produce.
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