Over small distances substances move by :

Options

A. diffusion
B. cytoplasmic streaming
C. Mass flow
D. both (A) and (B)

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks how substances move over small distances in plants. We need to evaluate the options provided to determine which processes are involved in this movement.

2. **Evaluating Option 1 - Diffusion**:
- **Definition**: Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration.
- **Relevance**: In plants, diffusion is a key process for the movement of substances such as gases (like oxygen and carbon dioxide) and water over short distances, such as within cells or between adjacent cells.
- **Conclusion**: This option is correct.

3. **Evaluating Option 2 - Cytoplasmic Streaming**:
- **Definition**: Cytoplasmic streaming, also known as cyclosis, is the movement of the fluid substance (cytoplasm) within a plant cell.
- **Relevance**: This process facilitates the distribution of nutrients, organelles, and other substances within the cell, effectively moving them over small distances.
- **Conclusion**: This option is also correct.

4. **Evaluating Option 3 - Mass Flow**:
- **Definition**: Mass flow refers to the bulk movement of substances, typically over longer distances, driven by pressure differences.
- **Relevance**: While mass flow is important for transporting nutrients and water throughout the plant, it is not primarily associated with the movement of substances over small distances.
- **Conclusion**: This option is incorrect.

5. **Evaluating Option 4 - Both A and B**:
- **Conclusion**: Since both diffusion and cytoplasmic streaming are correct methods for the movement of substances over small distances, this option is correct.

6. **Final Answer**: The correct answer is option 4 - Both A and B.

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