What are the cells that make the leaves curl in plants during water stress ?

Explanation

### Step-by-Step Solution:

1. **Identify the Question**: The question asks about the specific cells responsible for the curling of leaves in plants during water stress.

2. **Understand the Concept of Water Stress**: Water stress occurs when plants lose water faster than they can absorb it, leading to a decrease in turgor pressure within the cells.

3. **Identify the Specialized Cells**: The cells that are primarily responsible for the curling of leaves during water stress are known as **bulliform cells**.

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