Question

If a dried cobalt chloride paper is clipped on the under surface of a leaf its colour changes from blue to pink because

• A. It reacts with the chlorophyll of the leaf.
• B. The clipper puts a pressure on the paper.
• C. Paper is moistened by the transpiring water.
• D. It comes in contact with green leaf.

Answer 1

Answer: (C)

Paper is moistened by the transpiring water.

There is a change in the colour of cobalt chloride paper clipped on the lower surfaces of the leaf indicates loss of water vapour from this surface through transpiration. Cobalt chloride paper is pink when moist and blue when dry. The rate of loss of water is, however, more on the lower side than the upper side.