Question

Why are the stomata in most plants more numerous on the lower surface of a leaf instead of being on the upper surface ?

Answer 1

Stomata are more numerous on the lower side of the leaf to prevent transpiration. Transpiration is the loss of water through stomata, so, more stomata are found on the lower surface to prevent excessive loss of water. As the lower surface of leaf is not directly exposed to sun, rate is transpiration is low from the lower surface.