In progressive senescence, the leaves fall

Options

A. Immediately
B. Gradually
C. No falling
D. Leaf become permanently affixed

Answer

To solve the question regarding progressive senescence and the falling of leaves, let's break it down step by step.

### Step-by-Step Solution:

1. **Understanding the Terms**:
- **Progressive**: This term indicates a gradual change or development over time.
- **Senescence**: This refers to the process of aging in plants.

2. **Connecting the Terms**:
- Progressive senescence in plants means that the aging process occurs gradually, leading to various changes in the plant, such as the yellowing of leaves and the eventual dropping of leaves.

3. **Observing the Process**:
- In progressive senescence, the leaves do not fall off suddenly. Instead, they change color (often yellowing) and then fall off as part of the aging process.

4. **Evaluating the Options**:
- **Immediately**: This option suggests that leaves fall off suddenly, which is incorrect in the context of progressive senescence.
- **Gradually**: This option aligns with the definition of progressive senescence, where changes occur over time, making it the correct choice.
- **No falling**: This implies that leaves do not fall at all, which is also incorrect since falling leaves is a characteristic of senescence.
- **Leaf become permanently affixed**: This suggests that leaves remain attached indefinitely, which contradicts the nature of senescence.

5. **Conclusion**:
- Based on the explanations and evaluations, the correct answer to the question is that in progressive senescence, the leaves fall **gradually**.

### Final Answer:
The correct option is **gradually**.