Dark reaction of photosynthesis is

Options

A. Hill reaction
B. Calvin cycle
C. Cyclic photophosphorylation
D. Non-cyclic photophosphrylation.

Answer

**Step-by-Step Solution:**

1. **Understanding Photosynthesis**: Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose. It consists of two main stages: light reactions and dark reactions.

2. **Identifying the Types of Reactions**:
- **Light Reactions**: These reactions require light and occur in the thylakoid membranes of chloroplasts. They involve the absorption of light energy, water splitting (Hill reaction), and the production of ATP and NADPH.
- **Dark Reactions**: Also known as the Calvin cycle, these reactions do not require light directly and occur in the stroma of chloroplasts. They utilize ATP and NADPH produced in the light reactions to fix carbon dioxide into glucose.

3. **Analyzing the Options**:
- **Hill Reaction**: This is a light-dependent reaction that involves the splitting of water and is not a dark reaction.
- **Calvin Reaction (Calvin Cycle)**: This is a dark reaction that involves the fixation of carbon dioxide and does not require light, making it the correct answer.
- **Cyclic Photophosphorylation**: This process is light-dependent and involves the generation of ATP without the production of NADPH.
- **Non-Cyclic Photophosphorylation**: This is also a light-dependent process that produces both ATP and NADPH.

4. **Conclusion**: Based on the analysis, the dark reaction of photosynthesis is best represented by the Calvin reaction (C3 pathway).

**Final Answer**: The dark reaction of photosynthesis is the Calvin reaction (option B).

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