Question

What will be the result of the starch test performed on the leaf “A” shown in the diagram? Give an example of a plant with variegated leaves.

Answer 1

Hint: Starch test is done to find out the presence of carbohydrate in the sample. It is performed by using an Iodine solution. The test is known as the Iodine starch test. Starch test is used to check whether photosynthesis has occurred or not.

Complete answer:
To answer this question, we must know about the starch test.
In starch iodine test, the presence of carbohydrate or starch is inferred when the iodine solution turns blue black else absent.
This experiment is performed to demonstrate the importance of sunlight in photosynthesis. The plant was kept in the dark and the leaves turned pale yellow. On performing the starch iodine test on the pale yellow part of the leaf, the solution did not turn blue black.
Result: This proves that the starch is absent in the leaf. If the starch is absent then photosynthesis did not take place.
Variegated leaf-A variegated leaf is a leaf which contains white and green portions. The chlorophyll is only present in the green portion of the leaf. Example of such a leaf is Adam’s Needle, Chameleon plant.
Note: Plants prepare their food in the form of carbohydrate by the process of photosynthesis. The sunlight and chlorophyll are the limiting factors for the same without which photosynthesis cannot take place. The prepared food is stored in the form of starch.