Question

How would you test the presence of starch in leaves

Answer 1

In the presence of starch, iodine changes its color from brown to blue-black or purple. So, iodine is used to test the presence of starch.

Starch testing

Iodine solution is used to test leaves for the presence of starch. You need to:

1. heat a plant leaf in boiling water for 30 seconds (this stops its chemical reactions)
2. heat it in boiling ethanol for a few minutes (this removes most of its colour)
3. wash with water and spread onto a white tile
4. add iodine solution from a dropping pipette

After a few minutes, the parts of the leaf that contain starch turn blue-black.