Question

Explain the mechanism of opening and closing of stomata.

Answer 1

Stomata:

1. Stomata are the tiny apertures seen on the leaf epidermis.
2. Stomata can be seen in the light microscope.
3. Stomata can be found on stems and other plant components.

Structure of stomata:

1. Two guard cells surround each stoma.
2. The kidney-shaped guardians contain chloroplasts.
3. Each stoma has its own breathing chamber.

Mechanism of stomatal closure and opening:

1. The supply of sugar and starch in the guard cells determines the process of stomatal closure and opening.
2. The guard cells of the stomata contain sugar, which is generated by their chloroplasts in the presence of light.
3. The sugar gets solubilized and the guard cells' concentration is also increased.
4. Water enters guard cells by osmosis from surrounding cells due to the higher amount of cytoplasm in these cells. The stomata remain open as a result.
5. When there is no light, the sugar in guard cells turns to starch.
6. The starch is insoluble, so the guard cells have a lower concentration than the neighboring cells, and the neighboring cells osmotically remove the water from the guard cells, rendering them flaccid and the stomata close.