How would you test the presence of starch in leaves?

To test for the presence of starch in leaves, you can follow a simple procedure using iodine solution. This test is commonly used in biology to demonstrate photosynthesis in plants.

Materials Needed

• Green leaf (preferably from a plant that has been exposed to sunlight)
• Iodine solution
• Boiling water
• Alcohol (ethanol)
• Petri dish or small container
• Heat source (like a Bunsen burner or hot plate)

Steps to Follow

1. Boil the Leaf: Place the green leaf in boiling water for about 2-3 minutes. This step kills the leaf and breaks down cell membranes.
2. Alcohol Treatment: Carefully transfer the boiled leaf to a container with alcohol and heat it in a water bath for about 5-10 minutes. This removes chlorophyll, making the leaf pale.
3. Apply Iodine: Rinse the leaf in warm water briefly, then immerse it in iodine solution for a few minutes. The iodine will react with any starch present.
4. Observe the Color Change: Remove the leaf from the iodine and rinse it again. If starch is present, the leaf will turn a blue-black color.

What This Indicates

A blue-black color indicates that starch is present, confirming that photosynthesis has occurred in the leaf. If there is no color change, starch is not present.