Question

Enumerate the steps involved in testing a green leaf for the presence of starch.

Answer 1

Test to determine the presence of starch in a leaf:

• Dip a leaf in boiling water for a minute to kill the living cells.
• Boil the leaf in methylated spirit in a water bath to remove the chlorophyll, till the leaf turns pale blue and becomes hard and brittle.
• Now place the leaf in hot water to soften it.
• Place the leaf in a Petri dish and pour iodine solution over it.
• The appearance of a blue-black colour on the leaf is indicative of the presence of starch.
• The absence of starch is indicated by a brown colouration.