Nature Bulletin No. 557-A March 8, 1975
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation
Most people have heard of Chlorophyll. In past years a number of
products were widely advertised as preventives of tooth decay and bad
breath because they contained this substance. We have been told that it
is responsible for the green color in the leaves of trees, the grass on our
lawns, and the weeds in our gardens. What is this mysterious "green
Scientists know that chlorophyll is a complex chemical found as a green
pigment in almost all green plants from the simple one-celled algae to
those that have flowers and bear seeds. Further, that it enables them,
with the aid of energy from sunlight, to manufacture their own foods
from inorganic materials such as air, water and minerals -- and grow!
But nobody knows exactly how this is done. It is one of the mysteries of
life on this planet.
There are some plants that have no chlorophyll. Most of them are fungi
such as bacteria, plant rusts, yeasts, molds and mushrooms. However,
they are either parasites that get their food from the living bodies of
other creatures, or scavengers that get it from the decaying remains of
plants or animals. They cannot make their own food as green plants do.
Chlorophyll generally occurs in minute particles suspended in the cell
fluids of the leaves and other parts of plants. Only in primitive plants,
such as algae, is it ever found dissolved in cell fluids. It is known to be
a mixture of two pigments, Chlorophyll A and Chlorophyll B, with a
molecular structure identical with that of the hemoglobin molecule in
human blood, except that the latter has an iron atom and the chlorophyll
molecule has a magnesium atom.
Chlorophyll molecules are composed of five elements: carbon,
hydrogen, oxygen, nitrogen and magnesium. As a plant seed sprouts,
the first three come from its built-in food supply. Soon, however, they
are provided in water absorbed by its first rootlets, and carbon dioxide
taken from the air by its little leaves. Nitrogen and magnesium are also
obtained from the soil by its roots. Meanwhile, the young plant must
have sunlight. Iron and manganese, although not chemically a part of
chlorophyll, apparently are needed also in its formation but their part in
the process is not yet understood. In fact, how a plant, starting from a
seed, manufactures the chlorophyll upon which its life and growth
depends is another great mystery.
Sandwiched between the colorless upper and lower skins of a leaf, is a
tissue having layers of two different kinds of cells: column-like
"palisade" cells, and irregularly shaped spongy cells. Both contain
chlorophyll and it enables the leaf to perform its main job: the
manufacture of food. The green color of a plant comes from within and
not from its skin. The palisade cells are long and perpendicular to the
leaf surface. In leaves that grow horizontally, there is only an upper
layer of such cells; in plants with upright leaves, such as grasses, there
are two layers -- one next to each "skin." In all cases, their arrangement
is such as to receive the maximum amount of light.
Photosynthesis, the strange complicated process of manufacturing food
in leaves -- even by plants under water -- involves the use of carbon
dioxide, water, dissolved minerals and sunlight. Chlorophyll, using
those materials and that energy manufactures glucose, a sugar which is
used, and oxygen which is released. You and I and all life on earth
depend, in one way or another, upon this basic process in nature.
Can you thay that we depend on photothynthethith?
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Update: June 2012