Which statement best explains why `C_(4)` grasses often do better than `C_(3)` grasses in hot dry environments?

Answer

To determine why C4 grasses often perform better than C3 grasses in hot, dry environments, we can analyze the characteristics and adaptations of these two types of plants.

### Step-by-Step Solution:

1. **Understanding C3 and C4 Photosynthesis**:
- C3 plants utilize the Calvin cycle for photosynthesis, which can be inefficient under high temperatures and low CO2 concentrations due to a process called photorespiration.
- C4 plants, on the other hand, have a modified pathway that allows them to efficiently fix CO2 even in hot and dry conditions.

2. **Adaptations of C4 Grasses**:
- C4 grasses possess specialized anatomical features, such as Kranz anatomy, which helps them minimize photorespiration.
- They have a thicker cuticle and more chloroplasts, which aid in water retention and efficient photosynthesis.

3. **Stomatal Behavior**:
- C4 plants can maintain a higher rate of photosynthesis while minimizing water loss. They can keep their stomata partially closed during the hottest parts of the day, reducing transpiration.

4. **Turgor Pressure**:
- C4 grasses are capable of generating positive turgor pressure, which helps them maintain cell rigidity and function even under high temperature and drought conditions. This ability allows them to conserve water more effectively than C3 grasses.

5. **Conclusion**:
- Given these adaptations, C4 grasses are better suited for hot, dry environments, as they can photosynthesize efficiently while minimizing water loss. Therefore, the statement that best explains why C4 grasses do better than C3 grasses in such conditions is that C4 grasses generate a positive turgor pressure and perform better at high temperatures.

### Final Answer:
C4 grasses often do better than C3 grasses in hot, dry environments because they generate a positive turgor pressure and are more efficient at photosynthesis under high temperatures.

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