Dark reactions of photosynthesis occur in

Options

A. Granal thylakoid membranes
B. Stromal lamella membranes
C. Stroma outside photosynthetic lamellae
D. Periplastidial space.

Answer

**Step-by-Step Solution:**

1. **Understanding Photosynthesis**: Photosynthesis is the process by which plants produce food in the presence of sunlight and chlorophyll, using carbon dioxide and water.

2. **Location of Photosynthesis**: The site of photosynthesis in plants is the chloroplast, which contains the green pigment chlorophyll.

3. **Types of Reactions in Photosynthesis**: There are two main types of reactions that occur in photosynthesis:
- **Light Reactions**: These occur in the thylakoid membranes of the chloroplast and involve the conversion of light energy into chemical energy, producing oxygen, ATP, and NADH.
- **Dark Reactions**: Also known as the Calvin cycle, these reactions do not require light directly and utilize the ATP and NADH produced in the light reactions to convert carbon dioxide into glucose.

4. **Location of Dark Reactions**: The dark reactions occur in the stroma of the chloroplast, which is the fluid-filled space surrounding the thylakoids. This area is outside the photosynthetic lamellae.

5. **Evaluating the Options**: Given the options:
- Granulothylakoid membranes: Incorrect, as this is where light reactions occur.
- Stromal lamellar membranes: Incorrect, as this is not the primary site for dark reactions.
- Stroma outside photosynthetic lamellae: Correct, as this is where dark reactions take place.
- Periplastidial space: Incorrect, as it is not related to the dark reactions.

6. **Conclusion**: The dark reactions of photosynthesis occur in the stroma outside the photosynthetic lamellae.

**Final Answer**: The dark reactions of photosynthesis occur in the stroma outside photosynthetic lamellae (Option 3).

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