Desert grasses often roll their leaves due to presence of

Options

A. Oily surface
B. Bulliform cells
C. Spines
D. None of these

Answer

**Step-by-Step Solution:**

1. **Understanding the Question:**
The question asks why desert grasses often roll their leaves. This is a physiological adaptation to conserve water in arid environments.

2. **Identifying Possible Answers:**
The options provided are:
- A) Oily surface
- B) Bulliform cells
- C) Spines
- D) None of these

3. **Analyzing Each Option:**
- **A) Oily surface:** While some plants have an oily surface to reduce water loss, this is not the primary reason for leaf rolling in grasses.
- **B) Bulliform cells:** These are specialized cells found in the epidermis of monocot leaves (like grasses). They are large, thin-walled, and vacuolated, which allows them to change shape based on water availability.
- **C) Spines:** Spines are adaptations found in some plants to reduce herbivory and water loss, but they are not directly related to leaf rolling in grasses.
- **D) None of these:** This option can be ruled out as we have identified a relevant answer.

4. **Focusing on Bulliform Cells:**
Bulliform cells are responsible for the rolling of leaves in response to water scarcity. When water is abundant, these cells are turgid, keeping the leaves flat. In dry conditions, they lose water, causing the leaves to roll up, reducing the surface area exposed to the sun and minimizing water loss.

5. **Conclusion:**
The correct answer is **B) Bulliform cells** as they are directly responsible for the rolling of leaves in desert grasses due to their ability to respond to water availability.