Question

A portion of destarched leaf of a potted plant was covered with a black strip of paper. The plant was exposed to sunlight for six hours and then tested for starch. It was observed that :

• A. both covered and uncovered parts turned blue black
• B. both covered and uncovered parts turned brownish yellow
• C. only the uncovered part turned blue black
• D. only the covered part turned blue black

Answer 1

Answer: (C)

only the uncovered part turned blue black

• To show that sunlight is necessary for photosynthesis, first take a plant with destarched leaves.
• Cover a part of one of its leaves with black paper and place it in sunlight.
• After few hours, perform iodine test on this leaf.
• Part of leaf covered with black paper appears brown while the uncovered region turns blue-black.
• Portion of leaf uncovered showed presence of starch due to photosynthesis.

So the correct answer is option C.