BACKGROUND:
The most important characteristic of plants is
their ability to manufacture food . Typically this process, known as
photosynthesis, occurs primarily in the green leaves of plants.
Photosynthesis occurs only in the chloroplasts of plant cells because
these are the organs that contain the green pigment chlorophyll. The
rate of photosynthesis is dependent on light concentration, temperature,
water, and organic and inorganic materials available to a plant. Three
aspects of light are important for photosynthesis: intensity, quality,
and duration. Intensity depends on the amount of sunlight falling on a
given chloroplast per second. The rate of photosynthesis will increase
if the light intensity is increased. The water available to a plant also
influences the rate of photosynthesis.
Photosynthesis is the physical and chemical process involved in the
trapping of the sun's energy and the use of this energy to manufacture
food. Green plants utilize water and carbon dioxide and in the presence
of sunlight and chlorophyll manufacture food. Food-making normally
occurs in the leaf cells of a plant. Chlorophyll is the substance which
gives leaves their green color, and is found within the chloroplasts
(small green bodies in plant cells) of leaves. All the things needed by
a plant to manufacture food are transported to the leaves through the
roots and stems. The plant cells can convert sugar into starch for
storage or combine it with other materials to build proteins, vitamins,
or fats.
When the temperature gets cool it starts to shut down
photosynthesis. The chlorophyll needed for the process stops
and the green color goes away. The colors of orange and yellow
which are masked by the chlorophyll come through. The orange
is from the pigment molecule called carotene and the yellow is from
xanthophyll molecule. Some leaves also turn red, but the is
from the production of another molecule called anthocyanin.
PROCEDURE:
- Read the poem The Colors of Fall. This will
give students a background of how leaves turn from green when it is
producing food to the red, orange and yellow of fall (when
photosynthesis shuts down.
- The worksheet examines
photosynthesis via chemical equations (with words) and has the students
illustrate the equation in pictures using the symbols given. The key is
for the students to see how you can easily write down what is happening
in a simple equation.
- Point out to students to make a legend of each of the components
so their diagram can be interpreted. You may want to give the following
clues to help them out.
| carbon dioxide = |
|
| water = |
|
| sugar = |
|
| oxygen = |
|
| chlorophyll = |
 |
