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

Options

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

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks why grass leaves curl inwards during very dry weather. This indicates a response to water stress.

2. **Identifying Key Terms**:
- **Bulliform Cells**: These are specialized cells in the epidermis of leaves that help in water storage and play a crucial role in leaf movement.
- **Transpiration**: The process of water loss from plants through stomata.

3. **Analyzing the Options**:
- **Closure of Stomata**: While this is a response to reduce water loss, it does not directly cause the leaves to curl.
- **Placcidity of Bulliform Cells**: This option suggests that the bulliform cells lose turgor pressure and become flaccid, leading to the curling of leaves to minimize water loss.
- **Shrinkage of Air Spaces in Sponge Mesophyll**: This does not directly relate to the curling of leaves.
- **Thyloses in Vessels**: These are outgrowths that can block vessels but do not cause leaf curling.

4. **Choosing the Correct Answer**: The most appropriate reason for the curling of grass leaves during dry weather is the **flaccidity of bulliform cells**. When these cells lose water, they become flaccid, causing the leaves to curl inwards to reduce the surface area exposed to the atmosphere, thereby minimizing water loss through transpiration.

5. **Conclusion**: Therefore, the correct answer is **flaccidity of bulliform cells**.