thin-walled large cells present in the leaf epdiermis, and capable of contraction and expansion are

Options

A. guard cells
B. subsidiary cells
C. gland cells
D. bulliform cells.

Answer

To answer the question about the thin-walled large cells present in the leaf epidermis that are capable of contraction and expansion, we will analyze each option provided:

1. **Guard Cells**:
- Guard cells are modified epidermal cells that surround the stomata.
- They regulate the opening and closing of the stomata, which is crucial for the process of transpiration.
- However, guard cells are not completely thin-walled; they have thickened inner walls and thinner outer walls.
- Therefore, this option is incorrect.

2. **Subsidiary Cells**:
- These are also epidermal cells that are found surrounding the guard cells.
- They assist guard cells in the function of stomatal regulation but do not have the ability to contract or expand themselves.
- Thus, this option is also incorrect.

3. **Gland Cells**:
- Gland cells are specialized cells that secrete substances but do not have the capability of contraction and expansion.
- Therefore, this option is incorrect as well.

4. **Bulliform Cells**:
- Bulliform cells are large, thin-walled epidermal cells located on the adaxial (upper) epidermis of grass leaves.
- They are specifically designed to help in the rolling and unrolling of the leaf lamina, which allows them to contract and expand.
- This function is important for reducing water loss due to evaporation.
- Hence, this option is correct.

In conclusion, the correct answer to the question is **Bulliform Cells**.