Select the correct answer to the questions from the given options. (Do not copy the questions, write the correct answer only.)
The paper used to demonstrate unequal transpiration in a dicot leaf is:
Topic: Cobalt chloride paper
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Answer
(d) Cobalt chloride paper.
COBALT CHLORIDE PAPER is a water indicator: it is BLUE when dry and turns PINK when moist.
HOW THE EXPERIMENT WORKS: dry blue cobalt chloride paper is fixed to BOTH surfaces of a leaf. The paper on the LOWER surface turns pink much faster, because a dicot leaf has FAR MORE STOMATA on the lower epidermis than on the upper. That difference in speed demonstrates unequal transpiration.
WHY THE STOMATA ARE ARRANGED THIS WAY: the lower surface is shaded and cooler, so keeping the pores there reduces water loss while still allowing carbon dioxide in. The upper surface, exposed to the sun, carries a thicker cuticle instead.
Note that litmus paper tests acids and alkalis, not water — it is offered because it is the paper students know best.
Cobalt chloride paper.