Question

Pick out the wrong statement.
I. Guard cells expand on the inner side of the stoma, resulting in kidney-shaped cells.
II. The shape taken by the guard cells is independent of the cellulose microfibrils.
III. The unequal stretching of the guard cells allows the pore to form between the two guard cells.

• A. I and II
• B. Only II
• C. I and III
• D. I, II and III

Answer 1

The correct option is A I and II

Guard cells expand on the outer edges of the stoma, but not on the inner side. This results in kidney-shaped cells in dicot plants and dumb-bell shaped guard cells in monocot plants. An opening or pore between the two guard cells for the exchange of gases is formed as the guard cells expand.

The shape taken by the guard cells is dependent on cellulose microfibrils that fan out radially from the pore, somewhat similar to radial tires. The cellulose microfibrils are rigid and do not stretch when water has entered the cell.

The cell walls surrounding the stomatal opening are thickened, preventing that side of the guard cell from expanding. Therefore, when pressure in the cell increases due to water entry, guard cell does not widen, but rather the outer edge stretches disproportionately more than the inner edge. This unequal stretching allows the pore to form between the two guard cells.

Thus statement I and II are incorrect.