Dark reaction consists of

Options

A. `C_3` cycle
B. `C_4` cycle
C. CAM cycle
D. All of these

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 occurs mainly in the chloroplasts of plant cells.

2. **Two Main Reactions**: Photosynthesis consists of two main types of reactions:
- **Light Reactions**: These occur in the thylakoid membranes of the chloroplasts and require light. They convert solar energy into chemical energy, producing ATP and NADPH.
- **Dark Reactions**: Also known as the Calvin Cycle, these reactions do not require light directly and take place in the stroma of the chloroplasts. They utilize ATP and NADPH produced in the light reactions to synthesize glucose from carbon dioxide.

3. **Dark Reaction Processes**: The dark reactions involve several cycles, primarily:
- **C3 Cycle**: This is the most common pathway for carbon fixation, where carbon dioxide is fixed into a 3-carbon compound (3-phosphoglycerate).
- **C4 Cycle**: This pathway is adapted by some plants to efficiently fix carbon dioxide in hot and dry environments, producing a 4-carbon compound.
- **CAM (Crassulacean Acid Metabolism) Cycle**: This is a water-conserving pathway used by some plants in arid conditions, where carbon dioxide is fixed at night and used during the day.

4. **Products of Dark Reactions**: The main product of the dark reactions is glucose, which is an organic compound. This glucose can then be used by the plant for energy or stored as starch for later use.

5. **Conclusion**: Therefore, the dark reactions consist of the processes involved in the C3 cycle, C4 cycle, and CAM cycle, all of which ultimately lead to the production of organic compounds, primarily glucose.

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