Question

Cobalt chloride paper remains blue on the upper surface of the leaf but turns pink on the lower surface of the leaf. This proves that:

• A. There are more stomatal openings on the lower side of the leaf.
• B. There are less stomatal openings on the lower side of the leaf.
• C. There are more stomatal openings on the upper side of the leaf.
• D. There are no stomatal openings on the upper side of the leaf.

Answer 1

The correct option is A

There are more stomatal openings on the lower side of the leaf.

More transpiration occurs on the lower side of a leaf because there are more stomatal openings on the undersurface of the leaf. This can be proved by an experiment in which pieces of cobalt chloride paper are attached to the two sides of the leaf and held in position with the help of a glass slide and tied with the help of a rubber band. The piece of paper on the upper side of the leaf does not turn pink or takes a longer time than the paper on the lower side of the leaf which turns pink faster.