Question

1.Take two potted plants. Keep one potted plant in a dark room and other in the sunlight for a week.
After one week observe the difference in the colour of the leaves. Now, pluck a leaf from
both the potted plants and label them as A and B. Make an iodine test for the presence of starch.
Write your observations in case of both leaf A and leaf B.​

Answer 1

Explanation:

Iodine test is used to test for the presence of starch.

When a plant is kept in the dark for 72 hours it is denied light which is a condition necessary for photosynthesis.

Photosynthesis leas to formation of starch.

When an iodine test is carried out for the leaf of the plant kept in the dark, the columns of iodine remain unchanged.

This is because of the absence of starch.

However when an iodine test is performed on the leaf of the plant kept in the light, the colour of the I done solution turns blue black indicating the presence of starch in the leaf.