Question

How would you test the presence of starch in leaves?

Answer 1

Starch:

1. Starch is a polysaccharide made up of multiple monomers of glucose.
2. Starch is produced by plants during the process of photosynthesis.
3. Hence, starch is stored inside plant leaves.
4. The process to test the presence of leaves is explained below.

Requirements:

1. Sample plants.
2. Glass jar or beaker to dip the plant leaves.
3. Stove and saucepan to boil water.
4. Iodine solution for checking the presence of starch.
5. Ethyl alcohol to break down chlorophyll.
6. Tweezers to pick up leaves.

Procedure:

1. Grow a plant inside a dark room and another in normal sunlight.
2. Take a beaker containing ethyl alcohol and a saucepan full of water.
3. After 24 hours, place the ethanol beaker inside the saucepan and keep heating till it starts boiling.
4. Take the tweezers and hold the leaves to dip them inside the boiling water for about 2 minutes.
5. Then, dip the leaves inside the ethanol till it loses the green colour.
6. After that, place the leaf in a shallow dish and wait for it to cool.
7. Put some drops of iodine to see the presence of starch.

Observation:

It was found that the leaf kept in sunlight gets changed into a blue-black colour as it produces starch, whereas the plant kept in dark does not produce starch as it changes to reddish-brown.