A student observed in his school garden that leaves of some plants are folding at the evening when he is going to home and unfolded and expanded when he is coming to the school in the morning. Which part of the leaf is responsible for these changes

Options

A. Petiole
B. Stipules
C. Lamina
D. Pulvinous leaf base

Answer

**Step-by-Step Solution:**

1. **Observation**: The student notices that the leaves of some plants fold in the evening and unfold in the morning. This behavior is a response to environmental changes, particularly light and possibly temperature.

2. **Identifying Leaf Structure**: To understand which part of the leaf is responsible for this movement, we need to identify the main parts of a leaf:
- **Petiole**: The stalk that attaches the leaf to the stem.
- **Lamina**: The broad, flat part of the leaf.
- **Stipule**: Small leaf-like structures at the base of the petiole.
- **Pulvinus**: A thickened part of the leaf stalk (petiole) that can facilitate movement.

3. **Understanding Leaf Movement**: The folding and unfolding of leaves are often due to the movement of the pulvinus, which is a specialized structure that can change shape in response to environmental stimuli.

4. **Conclusion**: In this case, the part of the leaf responsible for the folding and unfolding is the **pulvinus**. It allows the leaf to respond to the changes in light and possibly other environmental factors, causing it to fold in the evening and unfold in the morning.

5. **Final Answer**: The part of the leaf responsible for these changes is the **pulvinus**.

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