Given below is the diagram of an experimental setup to study the process of Transpiration. Cobalt chloride papers are fixed on the upper as well as lower surface of the leaf. Answer the questions that follow: Given below is the diagram of an experimental setup to study the process of Transpiration. Cobalt chloride papers are fixed on the upper as well as lower surface of the leaf. Answer the questions that follow:
What is the aim of the experiment?
Topic: Aim of the cobalt chloride experiment
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Pick an option and check your answer. The full worked answer is below either way.
Answer
(a) To prove that more transpiration occurs from the lower surface of a dicot leaf..
The experiment demonstrates UNEQUAL TRANSPIRATION — that a dicot leaf loses far more water from its LOWER surface than from its upper.
THE REASON: a dicot leaf has FAR MORE STOMATA on the lower epidermis than on the upper. Since most transpiration is stomatal, the surface with more pores loses more water.
WHY THE STOMATA ARE ARRANGED THIS WAY: the lower surface is shaded and cooler, so placing the pores there reduces water loss while still admitting carbon dioxide. The upper surface, exposed to the sun, carries a thicker cuticle instead.
Cobalt chloride paper is used because it is a WATER INDICATOR, and fixing it to both surfaces at once makes the comparison direct.
To prove that more transpiration occurs from the lower surface of a dicot leaf..