Which of the following statements does not characterize photoperiodism?

Options

A. Mediated by florigen hormone
B. Conversion of shoot apex into reproductive apex
C. Red light is stimulatory in SDL, PDL and DNP for flowering
D. Photoperiodism stimulus is perceived by mature leaf

Answer

To determine which statement does not characterize photoperiodism, we need to analyze the characteristics of photoperiodism and the provided statements. Here’s a step-by-step solution:

### Step 1: Understand Photoperiodism
Photoperiodism is the response of plants to the relative lengths of light and dark periods. It is crucial for regulating flowering and other developmental processes in plants.

### Step 2: Identify Types of Photoperiodic Plants
1. **Long Day Plants (LDP)**: Require more than a certain critical duration of light to flower.
2. **Short Day Plants (SDP)**: Require less than a certain critical duration of light to flower.
3. **Day Neutral Plants (DNP)**: Flower regardless of the light duration.

### Step 3: Role of Florigen
Florigen is a hormone produced in the mature leaves of plants in response to light. It is transported to the shoot apical meristem to induce flowering.

### Step 4: Analyze the Statements
Now, let's examine the statements provided in the question:

1. **Mediated by Florigen hormone**: This is true as florigen is essential for the flowering process.

2. **Conversion of shoot apex into reproductive apex**: This is also true; florigen causes this conversion.

3. **Red light is stimulatory in short day plants, long day plants, and day neutral plants for flowering**: This statement is false. Red light is actually inhibitory for long day plants and can disrupt flowering in short day plants.

4. **Photoperiodic stimulus is preceded by mature leaves**: This is true; mature leaves are necessary for the perception of light and the synthesis of florigen.

### Step 5: Conclusion
The statement that does not characterize photoperiodism is the third one: "Red light is stimulatory in short day plants, long day plants, and day neutral plants for flowering."

### Final Answer
**The statement that does not characterize photoperiodism is: "Red light is stimulatory in short day plants, long day plants, and day neutral plants for flowering."**

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