Water stress causes stomata to (A)____ hence reducing the (B)_____ availability.

Answer

To solve the question, we need to understand the relationship between water stress in plants and the functioning of stomata, as well as how this affects the availability of certain resources for photosynthesis.

### Step-by-Step Solution:

1. **Understanding Water Stress**: Water stress in plants occurs when there is insufficient water supply to the roots or when transpiration is excessive. This can happen due to drought conditions or high salinity.

2. **Effect on Stomata**: When plants experience water stress, they respond by closing their stomata. Stomata are small openings on the leaves that allow for gas exchange, including the intake of carbon dioxide (CO2) and the release of oxygen (O2).

3. **Consequences of Stomatal Closure**: The closure of stomata reduces the amount of carbon dioxide that can enter the plant. Since carbon dioxide is a critical component for photosynthesis, its reduced availability directly impacts the plant's ability to produce food.

4. **Filling in the Blanks**:
- For (A), we can fill in "close" because water stress causes stomata to close.
- For (B), we can fill in "carbon dioxide" because the closure of stomata reduces the availability of carbon dioxide for photosynthesis.

### Final Answer:
Water stress causes stomata to **(A) close** hence reducing the **(B) carbon dioxide** availability.

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