Assertion:- Biosynthetic phase of photosynthesis is also termed as dark reaction.
Reason :- Biosynthetic phase is not directly dependent on light but it is supported by products of light reactions.

Explanation

Dark phase of photosynthesis involves the main process of carbon fixation to form glucose. This phase takes place throughout the day and not necessarily in night. Since it is in contrast to light phase that takes place in the presence of sunlight, it is called dark phase. Moreover, the dark phase depends on the products of light phase, namely ATP and NADPH. Therefore, it is more appropriately called light-independent phase rather than as dark phase.