Explanation:
1. Stomata are the openings on the leaf for the exchange of the water and air from the plant to the environment. It actually helps plants to breath, so it can also be seen as nostrills of the plants. They are present on either side of the leaves. Opening a stomata is like opening the doors for the exchange of the gases . This comes at a cost.
Due to sunlight and heat from the environment water content of the leaf is also remarkably lost when stomata opens, which is protected otherwise due to outer waxy layer of the leaf. To reduce this, most of the stomata are present on the lower surface of the leaves, as it will reduce the possibility of water loss due to high sunlight during the afternoon.
2. In aquatic plants you can find most of the stomata present on the upper surface of the leaf. As the plants float on the water surface, its lower epidermis is stuck to the water, hence respiration is least likely there as there is no contact of the stomata with the air.
