Question

Observe the diagram and answer the following;

a. Are these types of guard cells found in monocots or dicots?

b. Which of these shows a higher water content (i) or (ii)?

c. Which element plays an important role in the opening and closing of stomata?

Answer 1

a. Guard cells

The cells that surround the stoma and regulate its opening and closing are called the guard cells. Guard cells in monocots are found to be dumbbell shaped and in dicots they are kidney bean shaped.

Final answer: Dicots

b. Turgidity and flaccidity of guard cells

* When the guard cells become turgid, their thin walls get extended and thick walls become slightly concave to open the stomatal aperture.

* When the guard cells lose water and become flaccid, their thick walls revert back to their original position and close the stomatal aperture.

* So stomata in figure (i) has a higher water content because it is turgid.

Final answer: Figure (i) shows higher water content (turgidity)

c. Opening and closing of stoma

*Increased concentration of $K^{+}$ ions in guard cells causes a rise in osmotic pressure. Water gets absorbed from surrounding cells. It increases the turgor pressure and results in opening of the stomatal pore.

* Movement of $K^{+}$ ions out of the guard cells results in lower osmotic pressure and water moves out from guard cells to surrounding cells. Now the guard cells become flaccid and the stomatal pore is closed.

*So potassium ion is responsible for opening and closing of stomatal pore.

Final answer: Potassium ions