Why is stomata present in lower part of the leaf ?

Question

Why is stomata present in lower part of the leaf ?

Answer 1

First of all, it is present in only some of the plants, and not all, example aquatic plants.

For those with stomata below the leaf surface, it is to prevent water loss through evaporation. If the stomata were above the leaf, the water vapour would escape. But in this case, the water vapour tends to push upwards, but is not able to get out, thus preventing water loss. Even if water vapour manages to leave the leaf, it will condense against the leaf surface again, thus giving the tree the cooling effect. So it is just an adaptation.

Answer 2

In botany, a stoma (also stomate; plural stomata) is a tiny opening or pore, found mostly on the under-surface (epidermis) of a plant leaf, and used for gas exchange. The pore is formed by a pair of specialized parenchyma cells known as guard cells which are responsible for regulating the size of the opening. Air containing carbon dioxide enters the plant through these openings where it gets used in photosynthesis and respiration. Oxygen produced by photosynthesis in the chlorenchyma cells (parenchyma cells with chloroplasts) of the leaf interior exits through these same openings. Also, water vapor is released into the atmosphere through these pores in a process called transpiration.

Dicotyledons usually have more stomata on the lower epidermis than the upper epidermis. As these leaves are held horizontally, upper epidermis is directly illuminated. Locating fewer stomata on the upper epidermis can then prevent excess water loss.

Monocotyledons are different. Because their leaves are held vertically, they will have the same number of stomata on the two epidermes.

If the plant has floating leaves, there will be no stomata on the lower epidermis and they absorb gases directly from water through the cuticle. If it is a submerged leaf, no stomata will be present on either .

SO STOMATA ARE MORE IN NUMBERS ON THE LOWER OR THE VENTRAL SURFACE OF DICOT LEAF. IN MONOCOT THEY ARE EQUAL IN NUMBER

Answer 3

not always because stomata may be present on  the upper surface for example in plants found partially merged in water.

other plants have adapted to water loss so stomata are present on lower surface in them.