Dark reactions are called biosynthetic phase of photosynthesis.
Reason: Dark reactions do not directly depend on the presence of light but are dependent on the products of the light reaction, i.e., ATP and NADPH.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Assertion**: The assertion states that "dark reactions are called the biosynthetic phase of photosynthesis." This is true because dark reactions (or the Calvin cycle) are responsible for synthesizing glucose from carbon dioxide and the energy carriers produced in the light reactions.

2. **Understanding the Reason**: The reason provided states that "dark reactions do not directly depend on the presence of light but are dependent on the products of the light reaction, i.e., ATP and NADPH." This is also true. Dark reactions do not require light directly, but they rely on the ATP and NADPH produced during the light reactions.

3. **Analyzing the Relationship**: While both the assertion and reason are correct statements, the reason does not serve as a direct explanation for the assertion. The assertion explains what dark reactions are called, while the reason explains how they function without light.

4. **Conclusion**: Therefore, the final conclusion is that both the assertion and reason are correct, but the reason does not correctly explain the assertion.

**Final Answer**: Both assertion and reason are correct, but the reason is not the correct explanation for the assertion.

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