Question

How will you test a leaf for starch? Mention any precautions you will take.

Answer 1

Test for starch:

• Pluck one of the green leaves that have been exposed to sunlight.
• Boil that leaf in water for 5 minutes to soften it.
• Then put the leaf in a test tube containing alcohol. Now, gently place this test tube in a beaker of warm water till the alcohol starts boiling. The chlorophyll will slowly get dissolved in the alcohol and the leaf will start losing its green colour.
• Now, remove the alcohol by washing the leaf with warm water. Then spread the leaf over a white tile and add some iodine solution to it.
• Wash the leaf with water to remove the iodine solution and then hold it in light. The parts of leaf which have starch will turn blue-black.

Precautions

• Do not allow the water in the beaker to boil.