Who first discovered the effect of photoperiod on flowering?

Options

A. F. W. Went
B. Kurosawa
C. Yabuta and Cousins
D. Garner and Allard

Answer

To answer the question of who first discovered the effect of photoperiod on flowering, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Photoperiodism**:
- Photoperiodism refers to the physiological reaction of organisms to the length of day or night. In plants, it influences flowering and growth based on the duration of light exposure.

2. **Historical Context**:
- Various scientists have contributed to the understanding of plant hormones and their effects on growth and flowering. However, the specific discovery of photoperiodism is attributed to particular researchers.

3. **Identifying Key Scientists**:
- F.W. Wendt discovered the plant hormone auxin in 1928.
- Kurosawa discovered abscisic acid, another plant growth hormone.
- Yabuta discovered gibberellin in 1935, which is important for plant elongation.
- However, the key figures in the study of photoperiodism are **Garner and Allard**.

4. **Conclusion**:
- Garner and Allard conducted significant research on photoperiodism and published their findings in 1920. They are credited with the discovery of the effect of photoperiod on flowering in plants.

5. **Final Answer**:
- The correct answer to the question is **Garner and Allard**.