How will you test the presence of starch in green leaves?

To test the presence of starch in green leaves, following steps are followed:

1. Pluck a leaf from a plant which has been exposed to sunlight for a few hours.
2. Put it in a test tube containing alcohol. Place the test tube in a beaker containing water and heat the water. As the alcohol begins to boil, the chlorophyll dissolves in it and the leaf becomes pale.
3. Remove the leaf from alcohol and wash it in warm water.
4. Lay the leaf in a dish and put a few drops of iodine on it.

We will observe that the colour of the leaf changes to blue-black. This shows that starch is present in the leaf.