1. Water Potential

2. WATER POTENTIAL
Water potential measures water’s tendency to leave one place in favor of another

3. Calculating water potential
Ѱs + Ѱp = Ѱ
Solute potential
Adding solute decreases water potential
Pressure potential
Increasing pressure increases water potential

4. Ѱs =-iCRT i=ionization constant (number of ions solute forms in water)
C=concentration (mol/L)
R=pressure constant (.0831 liter bars/mol K)
T=temperature (C+273)

5. Ѱp Plant cells have cell walls
Turgor pressure pushes out on the cell wall
Limits expansion

6. Equilibrium
Water moves until the water potential outside the cell is equal to the water potential inside the cell

8. Practice problems
Calculate the water potential of a 1M sucrose solution at 22° C
Calculate the water potential of a cell that has a pressure potential of 4 and a solute potential of -5
What would happen to the cell if it were placed in the 1M sucrose solution?

9. The initial molar concentration of the cytoplasm inside a plant cell is 2M and the cell is placed in a solution with a concentration of 2.5M.
Calculate the water potential of the cell and of the solution
Predict which direction water will move based on your calculations
Predict what will happen to the pressure potential of the cell
What will be the water potential of the cell once the system has reached equilibrium