Question

Guard cells _______ during the day and ______ at night.

• A. open
• B. close

Answer 1

Stomata:

1. Stomata are tiny pores present on the surface of the leaf that regulates the flow of gases.
2. Guard cells are specialized cells surrounding the stomata.
3. They are triggered by sunlight and regulate the rate of transpiration by opening and closing of stomata by change in turgor pressure.
4. During day time, in the presence of light, the stomatal pore opens by taking in water by the process of osmosis and increases the turgidity of the cell.
5. During night time, in the absence of light, the stomatal pores close as they lose water and decrease the turgidity of the cell.

Final answer: Guard cells open during the day and close at night.