Question

6. A leaf of a potted plant kept in darkness for 48hours was smeared with Vaseline jelly
then exposed to sunlight for 8 hours. Explain why the test for this
negative​

Answer 1

A destarched leaf is when coated with vaseline from both sides, then it closes the stomata of the leaves. This stops transpiration, respiration and photosynthesis. Starch is a type of carbohydrate. If photosynthesis will not occur, then starch will not be formed. So, the test for starch will be negative as there will be the absence of starch in the leaf.