Describe an experiment to show that transpiration takes place mainly through the stomata on the lower surface of a leaf.

Four leaves of the same plant are taken. The first is left untreated, the second has petroleum jelly on its upper surface, the third on its lower surface and the fourth on both. They are hung up and watched. The leaf with jelly on the lower surface and the one with jelly on both wilt least, showing that most water is lost from the lower surface, where the stomata are more numerous.

No citable source has been recorded for this record. Treat it as practice material, not as fact.

Explanation

Cobalt chloride paper turning from blue to pink shows the same result more quickly.