Question

Using a PMS pressure bomb, it takes 1.4 MPa of pressure to force water from the cut end of a maple leaf. The same leaf is then crushed and the resulting sap is placed in an osmometer. The osmometer determines that the solute concentration in the leaf sap is 0.8 M at 25 OC. What are the values for water potential, turgor potential, and osmotic potential in this leaf?

Answer 1

Osmotic Potential is the tendency of water molecules to move from a hypotonic to a hypertonic solution. Turgor Potential is the pressure exerted by the sap. Water potential is the tendency of water to move from one region to other under influence of osmosis, gravity or mechanical pressure.

water potential = pressure potential (turgor potential) + solute potential ( osmotic potential)

Osmotic potential = c * r * t

c= concentration, R= Universal Gas constant, t= temperature in kelvin

Osmotic potential = -0.8 * 8.314 *298 = -1.982 MPa

Turgor Potential = 1.4 MPa

Water Potential = Turgor Potential + Osmotic Potential

=1.4-1.982 = -0.582