Question

Why upper surface of the leaf has fewer stomata.

Answer 1

Bcoz major transpiration takes place from the upper side of the leaf bcz it is more exposed to sunlight.So there are fewer stomata on the upper side of the leaf to prevent transpiration and prevent loss of  water...

Answer 2

the upper part of leaf have fewer stomata because on the upper part they are more exposed to sunlight and wind. There are many stomata at the lower part because it reduces the rate of evaporation as their is no much sunlight reaching their.