Question

Grass leaves curl inwards during very dry weather. Select the most appropriate reason from the following:

• A. Closure of stomata
• B. Flaccidity of bulliform cells
• C. Shrinkage of air spaces in spongy mesophyll
• D. Tyloses in vessels

Answer 1

The Correct Option is B

The question asks why grass leaves curl inwards during very dry weather. The correct answer is "Flaccidity of bulliform cells". Let's explore this step-by-step:

1. Understanding Bulliform Cells: Bulliform cells are large, bubble-shaped epidermal cells occurring in groups on the upper surface of the leaves of many grasses. These cells play a crucial role in the plant's response to environmental conditions, such as conserving water during dry weather.
2. Role of Bulliform Cells in Dry Weather: During periods of drought or dry weather, bulliform cells lose water and become flaccid. This loss of turgidity in these cells leads to the inward curling of the grass leaves. This curling helps in reducing the surface area exposed to the sun and wind, thereby decreasing water loss through evaporation and transpiration.
3. Exclusion of Other Options:
   • Closure of stomata: While stomata do close to reduce water loss, this doesn't directly cause leaves to curl inward.
   • Shrinkage of air spaces in spongy mesophyll: This is not a primary mechanism for leaf curling during dry conditions.
   • Tyloses in vessels: Tyloses are related to the blockage of xylem vessels, usually in response to injury or infection, and not directly related to leaf curling.
4. Conclusion: The inward curling of grass leaves during dry weather is primarily due to the flaccidity of bulliform cells, which helps conserve water by reducing transpiration.