Grass leaves curl inwards during very dry weather. Select the most appropriate reason from the following:
Answer: (B) Flaccidity of bulliform cells. Answer: (B) Flaccidity of bulliform cells.
- A.Closure of stomata
- B.Flaccidity of bulliform cells✓
- C.Shrinkage of air spaces in spongy mesophyll
- D.Tyloses in vessels
Correct Answer
(B) Flaccidity of bulliform cells
Solution & Explanation
Answer: (B) Flaccidity of bulliform cells. Solution: In grass (isobilateral, monocot) leaves, certain large, empty, colourless adaxial epidermal cells along the veins are called bulliform cells. When they are turgid (full of water) the leaf surface stays exposed; under water stress they become flaccid and pull the leaf surface so that the leaf rolls/curls inwards, reducing the exposed surface and minimising transpirational water loss. Stomatal closure also conserves water but does not cause the mechanical inward curling. NCERT Reference: NCERT Class XI, Ch 6 Anatomy of Flowering Plants, p.77, line ~22–23: "When they are flaccid due to water stress, they make the leaves curl inwards to minimise water loss."