The cells which help in rolling and unrolling of leaf lamina in grasses are :

Options

A. Complementary cells
B. Motor cells
C. Passage cells
D. Companion cells

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the specific type of cells in grasses that are responsible for the rolling and unrolling of the leaf lamina.

2. **Identifying the Cells**: The options provided are complementary cells, motor cells, passage cells, and companion cells. We need to determine which of these cells are involved in the movement of the leaf lamina.

3. **Researching Leaf Structure**: In grasses, the leaf structure includes specialized cells that respond to water availability. The rolling and unrolling of leaves is a mechanism to reduce water loss during dry conditions.

4. **Identifying the Correct Cells**: The cells that facilitate the rolling and unrolling of the leaf lamina are known as **motor cells**, specifically **bulliform cells**. These cells are located on the upper surface (adaxial surface) of the leaf.

5. **Function of Bulliform Cells**: Bulliform cells are hygroscopic, meaning they can absorb water. When the plant is well-hydrated, these cells become turgid, causing the leaf to unroll. Conversely, when the plant is under drought stress, these cells lose water, leading to the rolling of the leaf to minimize water loss.

6. **Conclusion**: Therefore, the correct answer to the question is **motor cells**, specifically referring to bulliform cells, which help in the rolling and unrolling of the leaf lamina in grasses.

**Final Answer**: The cells which help in rolling and unrolling of leaf lamina in grasses are **motor cells** (bulliform cells).

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