Question

The opening and closing of the stomatal pore depends upon

• A. Oxygen
• B. Wind velocity
• C. Water in guard cells
• D. CO${}_2$ concentration

Answer 1

The correct option is C Water in guard cells

Hint: Transpiration is the loss of water from a plant surface exposed to air as water vapor, primarily through stomata.

Part 1 - Definition - Stomata

• Stomata are tiny pores present on the surface of leaves of plants that help the plant to release water vapor during transpiration and to take in carbon dioxide and release oxygen during photosynthesis.

Part 2 - Structure of Stomata

• Stomata are the tiny pores present on the epidermal surface of leaves.
• Two kidney-shaped cells known as guard cells, guard the pores.
• Guard cells are adapted to their function of opening and closing the stomatal aperture, as the inner wall of the guard cell is thicker than the outer walls.
• Also, the specific arrangement of the microfibrils of the guard cells aids in the opening and closing of the stomatal aperture.

Part 3 - Mechanism of stomatal opening and closing

• The opening and closing of stomata result from turgidity changes in the guard cells.
• During the daytime, guard cells can perform photosynthesis, which leads to an increase in osmotic pressure.
• As a result, the guard cells absorb water from the neighboring cells and become turgid.
• The outer thin walls of guard cells are pushed out and the inner thicker walls are pulled inwards resulting in stomatal opening.

Part 4 - Conclusion

• From the above discussion, we can conclude that the opening and closing of stomata is controlled by turbidity changes in guard cells, which in turn depends on the amount of water present in the guard cell.

Final step: The opening and closing of the stomatal pore depends upon water in guard cells.