Question

Opening of stomata is due to
a. Turgidity of guard cells
b. Size of guard cells
c. Number of guard cells
d. Amount of CO2 in the atmosphere

Answer 1

Hint: Stomata are the small (microscopic) pores or openings in the plants found on the epidermis of leaves. Stomata are also present on a young stem and other plant parts in some plants. On the underside of the leaves stomata are generally more numerous. Stomata play a significant role in the exchange of gases and photosynthesis. It is surrounded by two guard cells.

Complete answer:
• The process of loss of water from aerial parts of the plant through stomata is known as transpiration.
• Guard cells manage the opening of the stomatal pore.
• When the water enters the guard cells, the guard cells become turgid.
• The thin outer wall in the turgid guard cells is pushed outside; it pulls the thicker inner wall outside.
• Due to this stomata opens.
• When the solute decreases in the guard cells, they become flaccid.
• The inner wall of guard cells goes back towards the stomata and this causes the closing of the stomata.
• The size of the guard cells is 20 micrometers in length and 9 micrometers in width.
• A stoma is surrounded by two bean-shaped guard cells surrounding the stomata.
• With the decrease in carbon dioxide concentration stomata opens and with an increase in the carbon dioxide concentration stomata closes.

Hence, the correct answer is option (A).

Additional information:
• Guard cells regulate extra water loss.
• Guard cells close during hot, windy, and dry days and open when conditions are more suitable for the exchange of gases.
• Opening of stomata depends on the water content of epidermal cells, temperature, light, and mineral elements.

Note: The opening and closing of stomata depend on the turgor pressure which is caused by the osmotic entry of water in the guard cells. When guard cells are turgid, stomata open and when they are flaccid, stomata close. The opening and closing of stomata regulate the rate of transpiration. The stomata open during the day and close during the night. Stomata permit the plant to give out oxygen and take carbon dioxide for photosynthesis.