Question

Write an activity to test presence of starch in leaf.​

Answer 1

Answer:

The hot water kills the leaf and the alcohol breaks down the chlorophyll, taking the green color out of the leaf. When you put iodine on the leaves, one of them will turn blue-black and the other will be a reddish-brown. Iodine is an indicator that turns blue-black in the presence of starch.

Answer 2

Answer:

Iodine solution test can be performed to check the presence of starch I leaf.

1. Detach a leaf from a destarched plant and dip it in boiling water for about 30 seconds so that cells are dead and no further chemical changes take place in them. Boiling also make the leaf cells more receptive in iodine solution.

2.Now boil the leaf in alcohol or methylated spirit in a water bath till it becomes colourless due to removal of chlorophyll.

3.Take out the leaf after decoloration. It becomes slightly brittle and hard. To soften it, dip it again in boiling water.

4.Spread the leaf on a white tile and pour iodine solution over it and observe.

Observation: The leaf does not turn blue black.

Inference: The iodine solution does not change colour because the leaf did not contain starch.