Select the incorrect statement about photoperiodism.

Options

A. The site of perception of light / dark duration are the leaves.
B. Flowering in certain plants depends not only on a combination of light and dark exposures but also their relative durations.
C. The hypothesised hormonal substance migrates from shoot apices to leaves for inducing flowering .
D. Shoot apices modify themselves into flowering apices prior to flowering .

Answer

To solve the question regarding photoperiodism, we need to analyze each statement provided and identify the incorrect one. Here’s a step-by-step breakdown:

### Step 1: Understand Photoperiodism
Photoperiodism is the physiological reaction of organisms to the length of day or night. In plants, it primarily influences flowering and other developmental processes based on the duration of light and darkness they are exposed to.

### Step 2: Evaluate Each Statement
1. **Statement 1:** "The site of perception of light or dark duration are the leaves."
- **Evaluation:** This statement is correct. Leaves are indeed the primary sites for the perception of light and dark durations in plants.

2. **Statement 2:** "Flowering in certain plants depends not only on the combination of light and dark exposure but also their relative duration."
- **Evaluation:** This statement is also correct. Flowering in plants is influenced by the duration of light and dark periods, distinguishing between long-day and short-day plants.

3. **Statement 3:** "The hypothesized hormonal substance migrates from the shoot apices to leaves for inducing flowering."
- **Evaluation:** This statement is incorrect. In reality, the hormonal substances (like florigen) migrate from the leaves to the shoot apices to induce flowering, not the other way around.

4. **Statement 4:** "Shoot apices modify themselves into the flowering apices prior to flowering."
- **Evaluation:** This statement is correct. The shoot apices do undergo modifications to become flowering apices as part of the flowering process.

### Conclusion
The incorrect statement about photoperiodism is **Statement 3**.

### Final Answer
**The incorrect statement about photoperiodism is:**
"The hypothesized hormonal substance migrates from the shoot apices to leaves for inducing flowering."

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