Question 38: How do the guard cells regulate opening and closing of stomatal pores?
Answer:
Stomata are the specialized structures that are responsible for the exchange of gases between the plant and the environment. Stomata consist of small pores which are surrounded by a pair of kidney shaped guard cells which helps in the regulation of stomatal apertures. The opening and closing of the stomata is caused by the changes in the turgidity of the guard cells. Process of opening and closing of stomata:-
Stomata opening occurs due to the osmotic entry of water into the guard cells. When the water level or turgidity increases within two guard cells the thin outer walls bulge out and they elongate themselves because of the microfibrils in the cell wall of the guard cells. This expansion pulls off the guard cells and the increased turgidity of the cell wall causes the stomata to open.
Closing of stomata involves the reverse process in which when the guard cells lose turgidity due to the water loss from the elastic inner walls helps to regain their original shape. Then the guard cell becomes flaccid and closes the stomata.
Diagram:
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