Question

Which of the following facilitates opening of stomatal aperture?

• A. Contraction of outer wall of guard cells
• B. Decrease in turgidity of guard cells
• C. Radial orientation of cellulose microfibrils in the cell wall of guard cells
• D. Longitudinal orientation of cellulose microfibrils in the cell wall of guard cells

Answer 1

The correct option is C

Radial orientation of cellulose microfibrils in the cell wall of guard cells

The correct option is C.

Explanation of correct option:

1. The tiny pores found on the surface of young green stems and leaves are stomata.
2. Each stoma is covered by two unique epidermal cells known as guard cells.
3. The shape of guard cells is kidney-shaped, which plays an essential role in the opening and closing of stomata.
4. The guard cells' cell walls' microfibrils work together to control the opening of the stomata.
5. The orientation of cellulose microfibrils takes place radially rather than longitudinally, which makes it easier for the stomata to open.

Explanation of incorrect options:

Option A:

1. The movement of water takes place inwards when the osmotic concentration of the guard cell enhances.
2. This makes the stomata to get open and thus water moves inside.
3. Due to the contraction of the outer walls of the guard cells, the closing of stomata takes place.

Option B:

1. The changes in the guard cell’s turgidity are accountable for the instantaneous opening and closing of stomata.
2. With the increase in turgidity within the two guard cells, the opening of each stomatal pore takes place.

Option D:

1. The opening of the stomata is mediated because of the coordination of the microfibrils, however, these microfibrils are not oriented longitudinally.

Final answer: The opening of the stomatal aperture takes place by the radial orientation of cellulose microfibrils in the guard cells’ cell walls.