Ag Experiment #6 Photosynthesis
Showing Photosynthesis In Plant Leaves
(This lab was featured in the March/April issue of Making a Difference)
Show students that photosynthesis is occurring in plants.
- 4-5 different plants (interior plants work better)
- Tin foil
- Hot plate (do not use an open flame because of the alcohol)
- Three pans (a pie plate works well for two of these pans)
This is a lab you can use to show that photosynthesis is taking place in the leaves of plants. Herbaceous plants work best for this experiment. The plants will need to be in a well-lighted area for 48 hours prior to the experiment. When we do this activity, we place the plants back into the greenhouse. We usually place the students in groups of two or three to do this exercise.
- Take a plant(s) and cover the upper one-half (closest to the stem) of 5-6 leaf surfaces with tin foil, leaving the bottom half of the leaf exposed to light.
- Place the plant in a well lighted area for at least 48 hours.
- On the day that the lab is to be completed, each group will need a hot plate and a pan partially filled with water. The water will need to be heated to a boiling temperature.
- Remove the leaves that were partially covered with foil from the plant. Remove the foil from the leaves.
- Boil the leaf in water for five to seven minutes to soften the cell walls. You need to boil the leaves until they feel soft.
- Then, boil the leaf in alcohol in a pan on an electric hot plate. The leaves should boil in the alcohol for about ten minutes or until they appear to change color. The alcohol should turn green as the chlorophyll is removed.
- Now, test the leaf for starch content. Place the leaf in a dilute iodine solution for about 10 minutes. Remove the leaf from this solution and rinse with water. Hold the leaf up to the light. The part of the leaf that was covered with foil should be transparent. There is no manufactured food in this part of the leaf. The iodine stains the food produced in the lower part of the leaf and it should not be transparent.