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Water Potential Review
A solution in a beaker has sucrose dissolved in water with a solute potential of
-0.3MPa. A flaccid cell is placed in the above beaker with a solute potential of -0.7MPa.
1) What is the pressure potential of the flaccid cell before it was placed in the beaker?
2) What is the water potential of the cell before it was placed in the beaker?
3) What is the water potential in the beaker containing the sucrose?
4) How will the water move?
5) What is the pressure potential of the plant cell when it is in equilibrium with the sucrose solution
outside?
6) Also, what is the cell’s final water potential when it is in equilibrium?
7) Is the cell now turgid/flaccid/plasmolysed?
8) What is the cell’s solute potential when it is in equilibrium?
9) Is the cell hypotonic or hypertonic with respect to the outside?
Solute potential (ψs) = –iCRT
i=
The number of particles the molecule will make in water; for NaCl this would be 2; for sucrose
or glucose, this number is 1
C=
Molar concentration (from your experimental data/problem)
R=
Pressure constant = 0.0831 liter bar/mole K
T=
Temperature in degrees Kelvin = 273 + °C of solution
You are asked to estimate if a certain species of plant could live in a salt marsh. You collect the
following data:
The overall Ψ of the soil (Ψsoil): -1.7MPa
Solute concentration of plant cell contents: 0.1M (assume i=2 for NaCl, and 13°C)
Pressure potential of the plant cells is: 1.9 MPa
10) Do you think the plant could grow in this environment? Why or why not? Show your work.