Stomata are open during the day because this is when photosynthesis typically occurs. Opening and closing of stomata occur due to turgor changes in guard cells. When guard cells are turgid, stomatal pores is open … Stomata take in C02 required for the photosynthetic activity during the day.

What causes stomatal pores to open?

Stomata are composed of two guard cells. These cells have walls that are thicker on the inner side than on the outer side. This unequal thickening of the paired guard cells causes the stomata to open when they take up water and close when they lose water.

How does stomatal pores open and close?

The opening and closing of stomata are controlled by the guard cells. When water flows into the guard cells, they swell up and the curved surface causes the stomata to open. When the guard cells lose water, they shrink and become flaccid and straight thus closing the stomata.