Question

In a free floating plant, the stomata are
(a) Absent
(b) Present on upper surface
(c) Present on both the surface
(d) Present on lower surface

Answer 1

Hint: The stomata in plants are enclosed by bean shaped cells called guard cells. Plants that float in water have their lower surfaces submerged in water.

Complete answer:
To solve this question, first we need to know about stomata. Stomata are tiny openings or pores in plant tissue that allow for exchange of gases. Stomata are typically found in plant leaves but can also be found in some stems. The opening and closing of the pore is regulated by the guard cells. As water flows through them, the guard cells swell allowing the stomatal pore to expand. The pore often closes as the guard cells shrink.

Additional information:Now, let us find the solution from the given options-
The plants that are submerged underwater have their roots fixed to the soil under water. The plants that remain underwater have no stomata as they remain underwater and the surface cells of the plants are capable of absorbing water, nutrients, and dissolved gases in the water.

Most floating aquatic plants have stomata on their upper leaf surfaces, and usually their stomata are permanently open. They can take in carbon dioxide from the air and release oxygen into the air. The exposed surfaces of the leaves have a waxy cuticle to control water loss to the atmosphere, like terrestrial plants.
The number of stomata in an isobilateral (often monocotyledonous) leaf are about equal on both the surfaces. Both sides of the leaves are exposed to direct sunlight. Hence, there is not much distinction on the number of stomata.

In dorsiventral (often dicotyledonous) leaf, the lower surface has more number of stomata as the upper surface of the leaf is exposed to direct sunlight. These are mostly seen in terrestrial plants to control the rate of transpiration.

Thus, the correct answer is option B, present on the upper surface.

Note:Apart from water vapour loss in transpiration, exchange of oxygen and carbon dioxide in the leaf also occurs through stomata. Stomata are usually open in daytime and close in the night.