Assertion : In some plants flowering depends only on a combination of light and dark exposure.
Reason : The site of perception of light or dark duration are the shoot apices of plants.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion
B. If both assertion and reason are true but reason is not the correct explanation of assertion
C. If assertion is true but reason is false
D. If both assertion and reason are false

Explanation

To solve the question, we need to analyze both the assertion and the reason provided.

### Step 1: Evaluate the Assertion
The assertion states that "In some plants flowering depends only on a combination of light and dark exposure." This statement is related to the concept of photoperiodism, which is the response of plants to the relative lengths of light and dark periods.

- **Analysis**: While it is true that flowering in some plants is influenced by light and dark exposure, it is not accurate to say that it depends "only" on this combination. The duration of light and dark periods is also crucial. For example, short-day plants require a longer duration of darkness to flower, whereas long-day plants require longer light periods. Therefore, the assertion is **false**.

### Step 2: Evaluate the Reason
The reason states that "The site of perception of light or dark duration are the shoot apices of plants."

- **Analysis**: This statement is incorrect. The primary site for the perception of light and dark durations in plants is the leaves, not the shoot apices. The leaves contain photoreceptors that detect light, and this information is then transmitted to the rest of the plant to regulate flowering. Therefore, the reason is also **false**.

### Conclusion
Since both the assertion and the reason are false, the correct answer to the question is that both the assertion and the reason are false.

### Final Answer
Both assertion and reason are false.

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