Which of the following facilitates opening of stomatal aperture?
Answer: (C) Radial orientation of cellulose microfibrils in the cell wall of guard cells. Answer: (C) Radial orientation of cellulose microfibrils in the cell wall of guard cells.
- 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
Correct Answer
(C) Radial orientation of cellulose microfibrils in the cell wall of guard cells
Solution & Explanation
Answer: (C) Radial orientation of cellulose microfibrils in the cell wall of guard cells. Solution: The inner wall of the guard cell (towards the pore) is thick and the outer wall is thin; the cellulose microfibrils are arranged radially rather than longitudinally. When the guard cells become turgid, this radial orientation makes the thin outer wall bulge outward and pull the inner wall apart, opening the pore. A turgidity increase (not decrease) drives opening. NCERT Reference: NCERT Class XI, Ch 6 Anatomy of Flowering Plants, p.72, line ~26: "The outer walls of guard cells (away from the stomatal pore) are thin and the inner walls (towards the stomatal pore) are highly thickened" (radial microfibril orientation underlies this differential wall behaviour during opening).