Why a green leaf is bleached before carrying out a starch test?

The starch content of a leaf is measured after it has been bleached by boiling in alcohol. The chlorophyll in the leaves is destroyed, and the cell wall is subsequently broken. The leaf's chlorophyll is bleached out so that it may take up the iodine solution and turn a dark blue or black color. This allows us to accurately detect the leaf's starch content.

Extra information:

The iodine test can determine whether or not leaves contain starch (carbohydrate).

Here are the procedures for determining whether or not leaves contain starch:

Step 1: Collect a green leaf from a plant that has been in direct sunlight for at least a few hours.

Step 2: Half-fill a beaker with water and bring it to a boil.

Step 3: Place the leaf in a pot of boiling water and let it sit there for a few minutes to soften the cell wall.

Step 4: Boil the leaf in alcohol to extract the chlorophyll.

Step 5: Immerse the leaf in hot water to loosen its cells.

Step 6: Next, test the leaf for starch by dropping a few drops of iodine solution onto it.

A blue-black hue develops on the leaf once iodine is added, indicating the presence of starch in the sample.


Simply Easy Learning

Updated on: 10-Oct-2022


Kickstart Your Career

Get certified by completing the course

Get Started