For a solution at atmospheric pressure, water potential is

Options

A. `Psi_(w) = Psi_(s) + Psi_(p)`
B. `Psi_(w) = Psi_(s)`
C. `Psi_(w) = Psi_(s) - Psi_(p)`
D. `Psi_(w) = 0`

Answer

To solve the question regarding the water potential of a solution at atmospheric pressure, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Water Potential**: Water potential (Ψw) is a measure of the potential energy of water in a system and is influenced by solute concentration and pressure. It can be expressed with the formula:
\[ Ψw = Ψs + Ψp \]
where:
- Ψw = Water potential
- Ψs = Solute potential (osmotic potential)
- Ψp = Pressure potential (turgor pressure)

2. **Consider Atmospheric Pressure**: At atmospheric pressure, the pressure potential (Ψp) is typically considered to be zero. This is because atmospheric pressure does not exert additional pressure on the water in the solution. Therefore:
\[ Ψp = 0 \]

3. **Substitute into the Water Potential Equation**: Given that Ψp is zero, we can simplify the water potential equation:
\[ Ψw = Ψs + Ψp = Ψs + 0 \]
Thus:
\[ Ψw = Ψs \]

4. **Conclusion**: For a solution at atmospheric pressure, the water potential is equal to the solute potential. Therefore, the water potential (Ψw) is determined solely by the solute concentration in the solution.

### Final Answer:
At atmospheric pressure, the water potential (Ψw) of a solution is equal to the solute potential (Ψs).

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