Select incorrect statement for Pressure Flow or Mass Flow Hypothesis

Options

A. it is accepted mechanism for the translocation of sugars
B. sugars sugar move into the companion cells and then into the living phloem sieve tube cells by active transport.
C. loading of sugar at the source produces a hypotonic condition in the phloem
D. loading of the phloem sets up a water potential gradient that facilitates the mass movement in the phloem.

Answer

### Step-by-Step Solution:

1. **Understanding the Pressure Flow Hypothesis**:
The Pressure Flow Hypothesis, also known as the Mass Flow Hypothesis, explains how sugars are transported in plants from the source (where they are produced) to the sink (where they are utilized or stored).

2. **Identifying the Source and Sink**:
- The source is typically the photosynthetic organs (like leaves) where sugars are produced.
- The sink is usually non-photosynthetic organs (like roots or fruits) where sugars are consumed or stored.

3. **Analyzing the Statements**:
- **Statement 1**: "It is an accepted mechanism for the translocation of sugar."
- This statement is correct. The Pressure Flow Hypothesis is widely accepted for explaining sugar transport.
- **Statement 2**: "Sugar moves into the companion cell and then into the phloem sieve tube cells by active transport."
- This statement is also correct. The loading of sugars into the phloem involves active transport.
- **Statement 3**: "Loading of sugar at the source produces a hypotonic solution in the phloem."
- This statement is incorrect. Loading of sugar increases solute concentration, creating a hypertonic solution, not hypotonic.
- **Statement 4**: "Loading of the phloem sides of water potential gradient that facilitates the mass movement in the phloem."
- This statement is correct. The loading of sugars creates a water potential gradient that drives the flow of water and sugars.

4. **Conclusion**:
The incorrect statement regarding the Pressure Flow Hypothesis is the third statement, which incorrectly states that loading of sugar produces a hypotonic solution in the phloem.

### Final Answer:
The incorrect statement for the Pressure Flow or Mass Flow Hypothesis is: "Loading of sugar at the source produces a hypotonic solution in the phloem."

---