The site of perception of light/dark duration are the

Options

A. Leaves
B. Shoot apical meristem
C. Bud
D. Roots

Answer

To solve the question "The site of perception of light/dark duration are the?", we will analyze the options provided and relate them to the concept of photoperiodism in plants.

### Step-by-Step Solution:

1. **Understanding Photoperiodism**:
- Photoperiodism refers to the response of plants to the length of day or night. It is crucial for processes such as flowering, where plants respond to the duration of light and darkness.

2. **Identifying the Role of Leaves**:
- The leaves are the primary site for the perception of light and dark durations. They contain photoreceptors that detect changes in light conditions, which is essential for the plant's response to photoperiodism.

3. **Hormonal Substance Formation**:
- Upon detecting light or dark durations, leaves produce a hormonal substance necessary for flowering. This hormonal signal is crucial for initiating the flowering process in response to the photoperiod.

4. **Migration of Hormonal Signals**:
- After the hormonal substance is formed in the leaves, it migrates to the shoot apical meristem, where it triggers the development of flowers.

5. **Evaluating Other Options**:
- **Shoot Apical Meristem**: While it is involved in flowering, it does not perceive light/dark duration directly.
- **Bud**: Buds do not play a role in the initial perception of light/dark duration.
- **Roots**: Roots are not involved in the perception of light and dark; they primarily function in nutrient and water absorption.

6. **Conclusion**:
- Based on the above analysis, the correct answer to the question is **Leaves**. They are the site where the perception of light/dark duration occurs, leading to the necessary hormonal changes for flowering.

### Final Answer:
**Leaves**