On 7/4/2005 4:28 AM Todd Fatheree mumbled something about the following:
"lgb" wrote in message
...

In article ,
says...

It seems that with higher CO2 levels,
these green things (we'll call them "plants") work overtime doing

something

called photosynthesis, which releases oxygen.


That's a common misconception. Plants "inhale" CO2 and "exhale" O when
light is falling on their leaves. When it is dark, the process is
reversed. O in and CO2 out. That's why aquarium keepers like me, with
heavily planted tanks, install an air bubbler that comes on when the
lights go out and off when the lights go on.


What this proves is that your aquarium is a poor model of the earth. On the
earth, there are more plants available during the summer months and at
latitudes closer to the equator. Therefore, there is a small net effect of
positive O2 creation.


It is true that deciduous trees have their leaves in seasons where
daylight hours exceed night hours, so they do produce a net increase in
O, but this does go down somewhat on cloudy days.

Since evergreens have "leaves" the whole year, their O vs CO2 tends to
be pretty much a wash.


So, according to your analysis, we can take the evergreens out of the
equation, which leaves a net positive effect on O2 from deciduous trees.

todd


Not only that, he's dead wrong about the process.

There are two parts to photosynthesis:

The Light Reaction happens in the thylakoid membrane and converts light
energy to chemical energy. This chemical reaction must, therefore, take
place in the light. Chlorophyll and several other pigments such as
beta-carotene are organized in clusters in the thylakoid membrane and
are involved in the light reaction. Each of these differently-colored
pigments can absorb a slightly different color of light and pass its
energy to the central chlorphyll molecule to do photosynthesis. The
central part of the chemical structure of a chlorophyll molecule is a
porphyrin ring, which consists of several fused rings of carbon and
nitrogen with a magnesium ion in the center.

The energy harvested via the light reaction is stored by forming a
chemical called ATP (adenosine triphosphate), a compound used by cells
for energy storage. This chemical is made of the nucleotide adenine
bonded to a ribose sugar, and that is bonded to three phosphate groups.
This molecule is very similar to the building blocks for our DNA.

The Dark Reaction takes place in the stroma within the chloroplast, and
converts CO2 to sugar. This reaction doesn't directly need light in
order to occur, but it does need the products of the light reaction (ATP
and another chemical called NADPH). The dark reaction involves a cycle
called the Calvin cycle in which CO2 and energy from ATP are used to
form sugar. Actually, notice that the first product of photosynthesis is
a three-carbon compound called glyceraldehyde 3-phosphate. Almost
immediately, two of these join to form a glucose molecule.

--
Odinn
RCOS #7
SENS(less)
SLUG

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