Module E. Photosynthesis

(Level of difficulty **)

Question: Why are plants green?

Materials you will need:
An outdoor or indoor plant with green leaves
Aluminum foil
Small scissors

Locate an indoor plant (violet, geranium, philofendron) or a tree outside (maple, oak, elm, tulip and many other broad-leaved trees would work) with green flat leaves
Prepare a piece of aluminum foil about 3x larger than the size of the leaf
Carefully wrap the piece of aluminum foil around the leaf to make a small flat cap or envelope (see pictures for suggestions on how to wrap and fold the foil), be careful not to break or damage the leaf
Leave the foil cap in place for 7 days
Unwrap and remove the foil and observe the change in the leaf color as compared to the unwrapped leaf

Helpful hints and suggestions:
It is a good idea to wrap several (3-5) individual leaves, so that you can compare the results across many leaves treated in the same way
You can choose to cut a small hole on the side of the foil cap to allow some light in; you can be creative as to what shape to cut out.

Expected results:
Leaves that were wrapped with foil did not get any light and turned yellow. The green pigment called chlorophyll [that make the plant appear green and allows the plant to capture light] breaks down in the dark, hence the loss of green color.  Light-grown plants use carbon dioxide found in the air and the energy of light to make sugars that are necessary for plant growth.  This process is called photosynthesis.
If the foil cap you placed on a leaf had a hole, the part of the leaf exposed to light would remain green. In other words, that section of the leaf kept its chlorophyll and was able to photosynthesize.

Follow-up questions:
Why do you think photosynthesis is important for plant growth?
What do you think will happen if the entire plant did not get any light?
Why do you think in the fall leaves lose their green color and turn yellow, orange or red?
Do you know the type of plant (the species) you did your experiment on?
Would the outcome of the experiment be different if you used leaves of another type of plant or tree variety?
What else do you know about photosynthesis? Take a look at the following links: