the term "photoperiodism" was proposed by or the phenomenon of photoperiodism in plants was discovered by

Options

A. Darwin
B. Lysenko
C. Arnon
D. Garner and Allard.

Answer

### Step-by-Step Solution:

1. **Understand Photoperiodism**: Photoperiodism is the phenomenon where plants respond to the length of day and night. It refers to how plants react to the duration of light and darkness they experience.

2. **Historical Context**: Initially, scientists believed that plants responded primarily to light. However, it has been established that the response is actually more closely related to the amount of darkness the plants are exposed to.

3. **Types of Photoperiodic Plants**:
- **Short Day Plants**: These plants flower when the days are short and the nights are long. An example of a short day plant is chrysanthemum.
- **Long Day Plants**: These plants require long days and short nights to flower. Examples include potato and spinach.
- **Day Neutral Plants**: These plants do not depend on the length of day or night for flowering. Examples include tomato and strawberry.

4. **Key Contributors**: The phenomenon of photoperiodism was studied and the term was proposed by scientists named Garner and Allard. They conducted experiments that helped classify plants based on their photoperiodic responses.

5. **Conclusion**: Therefore, the correct answer to the question of who proposed the term "photoperiodism" or discovered the phenomenon is **Garner and Allard**.