Select an incorrect statement for translocation of solutes

Options

A. P.R. Stout and D.R. Hoagland (1939) proved that mineral salts are translocated through xylem.
B. By feeding plants with heavy isotopes, it was shown conclusively that inorganic substances move up the plant through xylem.
C. Any solute conducted through the xylem is carried along with the ascending streams of water, which are pulled up through the plant by transpirational pull.
D. The rates at which inorganic solutes are translocated through the xylem vessels, correspond closely with the rates of translocation of water.

Explanation

To solve the question of selecting the incorrect statement regarding the translocation of solutes, we will analyze each of the given statements one by one.

### Step-by-Step Solution:

1. **Statement 1**: "P. R. Stout and D. R. Hoagland in 1939 proved that mineral salts are translocated through xylem."
- **Analysis**: This statement is correct. Xylem is responsible for the transport of water and mineral salts from the roots to other parts of the plant.

2. **Statement 2**: "By feeding plants with heavy isotopes, it was shown conclusively that inorganic substances move up the plant through xylem."
- **Analysis**: This statement is incorrect. The use of heavy isotopes does not conclusively demonstrate the movement of inorganic substances through xylem. Instead, radioisotopes are used for such studies because they are unstable and provide clear tracking of movement in the plant system. Heavy isotopes are stable and do not serve the same purpose.

3. **Statement 3**: "Any solute conducted through xylem is carried along with the ascending streams of water, which are pulled up through the plant by transpirational pull."
- **Analysis**: This statement is correct. The process of transpirational pull helps in the ascent of water in the xylem, and solutes are carried along with this ascending water stream.

4. **Statement 4**: "The rate at which inorganic solutes are translocated through the xylem vessels correspond closely with the rate of translocation of water."
- **Analysis**: This statement is also correct. The movement of inorganic solutes in the xylem is closely linked to the flow of water, as they are transported together.

### Conclusion:
After analyzing all the statements, the incorrect statement is **Statement 2**: "By feeding plants with heavy isotopes, it was shown conclusively that inorganic substances move up the plant through xylem."

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