In mass flow , various substance move independently according to their

Options

A. Size
B. Concentration gradient
C. Root pressure
D. Carrier proteins

Answer

**Step-by-Step Text Solution:**

1. **Understanding Mass Flow Hypothesis**: The mass flow hypothesis explains how substances, particularly the sap in plants, move through the phloem tissue. This movement is crucial for transporting nutrients and other molecules from the source to the sink.

2. **Identifying Source and Sink**: In this context, the source is where the substances (like sucrose, amino acids, hormones, and minerals) are synthesized, while the sink is where these substances are utilized or stored.

3. **Components of Sap**: The sap primarily contains various molecules, including sucrose, amino acids, hormones, and minerals. These components are essential for the plant's growth and development.

4. **Role of Concentration Gradient**: The movement of substances in mass flow is driven by the concentration gradient. At the source, the concentration of these substances is high, while at the sink, the concentration is lower. This difference creates a gradient that facilitates the movement of substances from areas of high concentration to areas of low concentration.

5. **Evaluating the Options**:
- **Size**: Incorrect, as the movement is not primarily based on size.
- **Concentration Gradient**: Correct, as this is the main factor driving the movement.
- **Root Pressure**: Incorrect, as root pressure does not directly influence the independent movement of substances in mass flow.
- **Carrier Protein**: Incorrect, as mass flow does not rely on carrier proteins for the movement of sap.

6. **Conclusion**: The correct answer to the question is that in mass flow, various substances move independently according to their concentration gradient.

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