Experiment:
To show that light is needed for photosynthesis.
You will need:
- A destarched green pot plant
- A strip of aluminium foil
- A Bunsen burner
- A tripod
- Wire gauze
- A beaker of water
- A test tube and test tube holder
- A half a test tube of alcohol
- A few drops of iodine solution.
Method:
- Destarch a pot plant by placing it in darkness for 48 hours. (This means that all starch (food) will be used up.)
- Wrap a strip of aluminium foil around part of a leaf. Draw a diagram showing where the foil is.
- Leave the plant in bright light for 6 hours.
- Remove the leaf and it's foil cover.
- Test it for starch: Boil some water in a beaker over a Bunsen burner.
- Submerge the leaf in the water for a minute- this kills it.
- Half fill a test tube with alcohol.
- Turn off the Bunsen burner and take the leaf out of the beaker of water.
- Put the leaf gently into the test tube of alcohol.
- Place the test tube into the still warm beaker of water and leave it for 5-10 minutes.
- Remove the test tube from the water with the test tube holder and very gently pick the leaf out of the alcohol.
- Dip the leaf into the warm water to soften it and then place it in an evaporating dish and cover it with iodine solution.
- Record the results of the starch test on your diagram of the leaf.
Result:
The areas which were exposed to light turned blue/black; the area covered with foil turned brown. Iodine turns blue/black in the presence of starch.
Conclusion:
Light is needed to carry out photosynthesis.