A plant cell with a Ψ_S of −0.65MPa maintains a constant volume when bathed in a solution that has a Ψ_S of −0.30MPa and is in an open container. The cell has a
a. Ψ_P of +0.65MPa
b. Ψ of −0.65MPa
c. Ψ_P of +0.35MPa
d. Ψ_P of 0 MPa

Verified step by step guidance

1. Understand the concept of water potential (Ψ), which is the sum of solute potential (ΨS) and pressure potential (ΨP). The formula is Ψ = ΨS + ΨP.
2. Recognize that the plant cell maintains a constant volume, indicating that the water potential inside the cell is equal to the water potential of the surrounding solution.
3. Given that the solute potential (ΨS) of the cell is −0.65 MPa, and the solute potential of the surrounding solution is −0.30 MPa, calculate the pressure potential (ΨP) of the cell using the formula Ψ = ΨS + ΨP.
4. Since the cell is in an open container, the pressure potential of the surrounding solution is 0 MPa. Therefore, the water potential of the solution is Ψ = ΨS + ΨP = −0.30 MPa + 0 MPa = −0.30 MPa.
5. Set the water potential of the cell equal to the water potential of the solution to find the pressure potential of the cell: Ψ(cell) = Ψ(solution). Substitute the known values into the equation: ΨS(cell) + ΨP(cell) = ΨS(solution) + ΨP(solution).

Key Concepts

Water Potential (Ψ)

Water potential (Ψ) is a measure of the potential energy in water, influencing the movement of water in plant cells. It is determined by solute potential (ΨS) and pressure potential (ΨP). Water moves from areas of higher water potential to lower water potential, and understanding this concept is crucial for analyzing water movement in plant cells.

Solute Potential (ΨS)

Solute potential (ΨS), also known as osmotic potential, is the component of water potential that accounts for the effect of solute concentration. It is always negative or zero, as solutes lower the water potential. In the given question, the solute potential of the plant cell and the bathing solution are key to determining the pressure potential needed to maintain constant cell volume.

Pressure Potential (ΨP)

Pressure potential (ΨP) is the component of water potential that results from the physical pressure exerted on water in a cell. It can be positive, negative, or zero, and is crucial for maintaining cell turgor and volume. In the question, calculating ΨP helps determine the balance between solute potential and the external solution to keep the cell's volume constant.