The steps below are involved in the testing of a leaf for starch. Study them carefully and answer the…

Analyze the question: You are asked to put the four steps of the starch test on a leaf in the correct order.

Concept: The starch test has a standard procedure:

1. Boil the leaf in water (Step III). This kills the leaf, stops enzyme action, and softens the leaf and makes the cells permeable.
2. Decolorize the leaf (Step I). Put it in hot ethanol (alcohol) in a water bath to remove chlorophyll. Never heat ethanol directly, because it is flammable.
3. Dip the decolorized leaf in warm water (Step II). The leaf is brittle and hard after the alcohol, so warm water softens it and rinses off the ethanol.
4. Add iodine solution (Step IV). Starch turns the leaf blue-black. If there is no starch, the iodine stays brown or yellow-brown.

Solution: The correct order is III → I → II → IV.

Checking the options:

• A: Decolorizing a leaf that has not been boiled first is wrong.
• B: Boiling comes first, but the order then goes straight to warm water before decolorizing, which is wrong.
• C: Warm water comes first, which is wrong.
• D: III, I, II and IV, which matches the correct procedure.

Tip: Remember the order as "Boil, Bleach, Soften, Stain." Boil the leaf, remove the color (chlorophyll), soften it in warm water, then stain it with iodine.