The force of tension cohesion exceeds root pressure on a

Options

A. Rainy day
B. Foggy morning
C. Sunny day
D. Full moon night

Answer

To solve the question regarding when the force of tension cohesion exceeds root pressure, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concepts**:
- **Tension Cohesion**: This refers to the forces that help water move from the roots to the leaves of a plant. It is primarily driven by transpiration, where water evaporates from the leaves, creating a negative pressure that pulls water upward.
- **Root Pressure**: This is the pressure exerted by the roots of the plant to absorb water from the soil. It is generally lower than the tension created during transpiration.

2. **Identify the Conditions**:
- The question asks under which climatic conditions the force of tension cohesion exceeds root pressure. This typically occurs when transpiration rates are high.

3. **Analyze the Options**:
- **Rainy Day**: During rainy conditions, transpiration is usually low due to high humidity and water availability.
- **Foggy Morning**: Similar to rainy days, foggy conditions also lead to reduced transpiration.
- **Sunny Day**: On sunny days, the temperature is high, leading to increased evaporation of water from the leaves, thus increasing transpiration rates.
- **Full Moon Night**: Moon phases do not significantly affect transpiration rates.

4. **Conclusion**:
- The highest rate of transpiration occurs on sunny days due to increased temperature and sunlight, which leads to a greater force of tension cohesion. Therefore, the force of tension cohesion exceeds root pressure on a **sunny day**.

### Final Answer:
The correct answer is **sunny day**.

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