Question

why do few plants have stomata on the upper side of the leaf?

Answer 1

aquatiC plants have stomata only on the top part of the leaf as the underside of the leaf rests on the surface of the water and the rest of the plant is submerged.Since the plant is submerged in water the plant is not threatened by drought or have to close its stomata during the high heat of the day to conserve water.  However, the lily can still exchange gases with the stomata on the top of its leaf and able to perform photosynthesis. Hydrophytes (ex. water ferns) are submerge aquatic plants that do not have stomata. Instead of stomata, the plants surface cells are capable of absorbing water, nutrients, and dissolved gases in the water.

Answer 2

 Stomata are found on the upper epidermis because they allow direct exchange of gases between the leaf and the atmosphere