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 "Who first discovered the effect of photoperiod on flowering?" we can follow these steps:

### Step 1: Understand the concept of photoperiodism
Photoperiodism is the response of plants to the relative lengths of light and darkness in a 24-hour cycle. It significantly influences various developmental processes in plants, especially flowering.

**Hint:** Remember that photoperiodism is crucial for understanding how plants respond to seasonal changes.

### Step 2: Identify the scientists involved in the discovery
The question asks for the first discoverer of photoperiodism. The key scientists associated with this discovery are Garner and Allard.

**Hint:** Focus on the names of scientists who are known for their contributions to plant biology and photoperiodism.

### Step 3: Recall the year of the discovery
Garner and Allard conducted their research and proposed the concept of photoperiodism in 1920. They studied the Maryland mammoth variety of tobacco to demonstrate their findings.

**Hint:** Pay attention to the historical context and the specific plant variety used in their experiments.

### Step 4: Understand the implications of their findings
Garner and Allard showed that by manipulating light exposure (either increasing or decreasing light hours), they could induce flowering in plants. This led to the classification of plants into categories based on their light requirements: short-day plants, long-day plants, and day-neutral plants.

**Hint:** Consider how their findings impacted agricultural practices and plant breeding.

### Step 5: Choose the correct answer
Based on the information gathered, the correct answer to the question is "Garner and Allard."

**Hint:** When answering multiple-choice questions, eliminate options that do not align with the historical context or scientific contributions.

### Final Answer:
The first discovered the effect of photoperiod on flowering is **Garner and Allard** in 1920.