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Re: [streak] swoosh seedlings

little green in the leaves will grow less - or slover - because they
have less photosynthesis production of 'food for the plant'? Only the green
part of the leaves will make chlorophyll needed for plantgrowth?????
>Or ... ?

Ok I started to write up something but since I didn't want anyone to
descypher my terminalogy (and misspellings) I found a fairly descent article
on it...  so if someone wants to do a home test and post the results of the
cholorphyll for everyone well go for it (if I get the time I may even do


Green is for Growth

In an actively growing plant, the leaves are generally green.  There are
exceptions, of course, such as indian pipes which is completely white, and
certain ornamental plants which have anything from yellow to purple leaves
or even several colors at once.  Even in ornamental plants with different
colored leaves, like Coleus, there is some green hidden behind the myriad
other colors.

    The chemical structure of chlorophyll

The green present in most leaves is caused by the presence of the pigment
chlorophyll.   To a plant, each chlorophyll molecule is like a small power
generating plant.   It is a complex ring-shaped molecule with a magnesium
atom in the middle of it.   Chlorophyll absorbs light from the sun and then
uses the absorbed energy to fuel the chemical reactions required to take
carbon dioxide from the atmosphere and turn it into sugar.  The actual
chemistry of these reactions represents one of the wonders of nature.

The first step in the process involves the splitting of water into hydrogen
and oxygen, a process which ordinarily requires electricity.  Plants
accomplish this feat with sunlight as the sole energy source.  This first
step is important not only for the plant, but is also to all life on earth,
because this is the ultimate source of all the oxygen we breathe.  The
hydrogen from the split water molecules is then used in a series of steps,
somewhat analogous to sending electricity through a wire, to produce some
high energy molecules (ATP and NADPH, to be precise).  These high energy
molecules are then used as the energy source for the set of chemical
reactions that take carbon dioxide from the atmosphere and turn it into
sugar.  The entire process, therefore, takes light energy and transforms it
into chemical energy while at the same time producing oxygen.  This process
is usually referred to as photosynthesis by botanists and other scientists.

Helper Pigments

As important as chlorophyll is to photosynthesis, it is not the entire
story.   Light from the sun may appear white to us, but it is actually
composed of all the colors of the rainbow.  We observe this fact all the
time without realizing it.   Consider a red piece of paper.  The red color
that we see is a result of the paper reflecting the red components of the
light striking it, while all the other colors of light are being absorbed.
Chlorophyll behaves this way as well.  The green color of chlorophyll is the
result of certain colors being absorbed, in this case mostly reds and
certain blues, while others are reflected, mostly yellows, oranges and
certain blues.  The mixture of yellows, oranges and blues appear as green.
What this means to photosynthesis is that if chlorophyll were the only light
absorbing pigment in a plant a lot of the energy in light would be lost.  To
help harvest these other colors of light, leaves have helper pigments,
called accessory pigments by botanists.

The most common of these helper pigments are carotenoids, which are related
to b-carotene, the pigment that gives the orange color to carrots.  They are
complex chain-like molecules, although their structure is simpler than
chlorophyll and they don't contain any metal atoms like the magnesium in
chlorophyll.  Carotenoids range from yellow to orange in color and absorb
some of the blue and green colors that chlorophyll cannot.  The energy from
the light that is absorbed is then passed on to chlorophyll molecules.
Another light yellow colored group of pigments, called xanthophylls (the "x"
is pronounced like a "z"), also assist in absorbing some of the blue and
green colors of light.   In addition to absorbing colors not absorbed by
chlorophyll, they also help protect chlorophyll from destruction.  A certain
amount of chlorophyll is always being degraded by light, and without helper
pigments even more would be destroyed.

Normally these helper pigments are not visible, because the large amount of
chlorophyll mask them.  One way to confirm their presence is to extract
pigment from a leaf and then separate the different pigments by a process
called chromatography.  To do chromatography properly takes a special kind
of paper and organic solvents.  The pigment is soaked into the paper in a
narrow band and then is put into a closed container with the bottom of the
paper resting in the solvent.  As the solvent climbs up the paper the
pigments also travel up the paper.  The different pigments become visible
because each pigment travels at a different rate.   Using chromatography it
has also been discovered that there is more than one kind of chlorophyll.

You can try a very simple kind of chromatography at home using very porous
paper, acetone and rubbing alcohol.  Grind the leaves up in some acetone to
extract the pigments.  Transfer some of the green liquid to the paper,
preferably in a very narrow line just above the base of the paper.  Let the
liquid dry.  Put some rubbing alcohol in a large jar with a lid.  Make the
paper into a tube shape, using a stapler to retain the shape.  Put the tube
of paper into the jar, making sure that the rubbing alcohol is shallow
enough not to submerge the line of pigment on the paper.  After several
minutes the rubbing alcohol will climb the paper.   When it reaches the top,
take the paper out and you should see from two to four bands of color, one
or two green and one or two yellow.


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