Download Photosynthesis Involves Several Things: • Capturing the sun`s

Table 3: Light and Photosynthesis
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Photosynthesis Involves Several Things:
• Capturing the sun's energy (different wavelengths of light) using plant
pigments
• Gas (carbon dioxide) entering through openings in the leaves (stomates).
• Water being broken into oxygen (which leaves through openings in the
leaves) and hydrogen.
• The converted sun's energy is used to make sugars (carbohydrates)
Let's look at each of these events.
1) The sun's light is made of many different colors or wavelengths. The color of
the light depends on how close together the "waves" of light are.
We learned when we studied light, that light waves can be reflected or absorbed.
When certain wavelengths of light are reflected, then they appear as that color. For
example, a red shirt is actually absorbing all the wavelengths of light EXCEPT
FOR red! The red wavelengths are being reflected and so the shirt looks RED!
Look at light through the prism. You can see that light is split into many different
colors (wavelengths).
The colors of the spectrum are: red, orange, yellow, green, blue, indigo, and violet
(ROYGBIV)! See if you can see all of the colors.
What color light is a green plant reflecting? Absorbing?
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If a plant need to absorb the sun's light for photosynthesis, then which color of light
is it NOT absorbing?
'-..---Soa plant has to have a way to absorb as much of the sun's energy as it can. It uses
pigments or colored molecules to capture as many of the sun's rays as it can.
Pigments are organized into special groups called photosystems.
What color do you think the main pigment of plants is?
Green! That's why plants look green! They have a pigment called chlorophyll that
reflects green light!
However, there are other pigments in leaves and other plant parts that are different
colors. They are different colors so that they can absorb different parts of the sun's
light. What color of light would a red pigment NOT absorb?
These pigments are called accessory pigments. Usually these pigments are covered
'-----up because there is SO MUCH of the green pigment chlorophyll that all we see is
green. However, these other colored pigments are also in the leaf absorbing other
parts of the sun's light. In the fall, when it gets cold, chlorophyll goes away and
what we see remaining are all the other beautifully colored pigments! That's why
leaves change colors in the fall!
Take a plant part and mash it against the paper. What color pigments do you see?
Carbon dioxide is a colorless gas. When we breathe out, we breath out carbon
dioxide. Although plants also release carbon dioxide (in a special process called
cellular respiration), they take in large amounts of carbon dioxide through special
openings in their leaves called stomates. Stomates are surrounded by kidney bean
shaped cells called guard cells. These guard cells can open and close to allow
carbon dioxide in or oxygen out.
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Look through the microscope and draw the guard cells that you see.
To show that we do breathe out carbon dioxide, place a small amount of.water in
the test tube. Add a drop of pH indicator to the water. Take a clean straw and blow
Into the water. You should see a color change as carbon dioxide leaves your lungs
and is converted to acid in the water!
Look at the leaves of the aquatic plant on the table. Do you see bubbles on the
plants leaves?
What gas do you think is in the bubbles?
Is the oxygen produced in photosynthesis?
The sun's energy is processed and used to make the carbon dioxide into sugar! A
sugar molecule looks like a smashed stop sign. Sometimes plants store sugar in
long chains (polymers). One example of stored sugar is STARCH!
-~.-/Y
our mom may use starch in certain recipes.
We can test for starch by adding iodine to a plant part.
Place a drop of iodine on a small piece of potato. What happens?
Do you think starch is stored in potatoes?
Where do you fmd potatoes on the food chain?
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