Leaves of many grasses are capable of folding and unfolding because they

Options

A. Are very thin
B. Are isobilateral
C. Have specialised bulliform cells
D. Have parallel vascular bundles.

Answer

To answer the question "Leaves of many grasses are capable of folding and unfolding because they:", we need to analyze the options provided and understand the role of specific cells in grass leaves.

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks why the leaves of many grasses can fold and unfold. This implies that there is a specific structural or functional feature that allows for this movement.

2. **Analyzing the Options**:
- **Option A: Very Thin**: While many grass leaves are thin, this characteristic alone does not explain the folding and unfolding mechanism.
- **Option B: Isobilateral**: Isobilateral leaves have the same structure on both sides, but this feature does not relate to the folding and unfolding capability.
- **Option C: Have Specialized Bulliform Cells**: Bulliform cells are specialized cells found in the epidermis of grass leaves. They are large, thin-walled cells that can change shape based on turgor pressure. When these cells lose water, they collapse, causing the leaf to fold. When they regain water, they expand, allowing the leaf to unfold.
- **Option D: Have Parallel Vascular Bundles**: While vascular bundles are important for transporting water and nutrients, they do not directly contribute to the folding and unfolding of leaves.

3. **Identifying the Correct Answer**: Based on the analysis, the correct answer is **Option C: Have Specialized Bulliform Cells**. These cells are responsible for the folding and unfolding of grass leaves due to changes in turgor pressure.

4. **Conclusion**: The leaves of many grasses are capable of folding and unfolding primarily because they contain specialized bulliform cells that respond to water availability.