What is the characteristic shape of guard cells in the stomatal apparatus of grass leaves (monocotyledons)?
Answer and explanation
Correct answer: B. Dumbbell-shaped
- Step 1: In typical dicot leaves, the guard cells flanking the stomatal pore are crescent- or kidney-shaped (reniform), with thick inner walls and thin outer walls.
- Step 2: In grasses and other monocots, the guard cells have a distinctive dumbbell shape, with bulbous ends and a narrow, thickened middle region.
- Step 3: This morphology allows rapid turgor-driven opening and closing of the stomatal aperture.
Answer
Dumbbell-shaped
Why not the others: 'Kidney-shaped (bean-shaped)' is the hallmark of dicot guard cells; 'Spherical' and 'Stellate' do not occur in stomatal guard cells.
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