Take two potted plants of the same kind. Keep one in the dark for 3 to 4 days and the other in sunlight. Perform the iodine test with the leaves of both the plants as given below. Now leave the pot which was earlier kept in the dark, undisturbed for 3 – 4 days and perform the iodine test again on its leaves.
Iodine test:
Put iodine solution on the leaf .
Observation:
Blue-black colour will be observed on the leaves of the plant kept in sunlight, which indicates the presence of starch.
Blue-black colour will not be observed on the leaves of plant kept in the darkroom. This indicates the absence of starch.