Water movement through membranes

Plant Physiology

UNI 2009

Pressure difference

Pipe #1

Pressure Potential = +1 barSolute Potential = -2 bars

Membranepasses water only

Pipe #2

Pressure Potential = +3 barsSolute Potential = -2 bars

Which way does the water move?

Pressure difference

Pipe #1

Pressure Potential = +1 barSolute Potential = -2 bars

Membranepasses water only

Pipe #2

Pressure Potential = +3 barsSolute Potential = -2 bars

Water (only) moves from higher to lower potential.

Solute difference

Pipe #1

Pressure Potential = +1 barSolute Potential = -2 bars

Membranepasses water only

Pipe #2

Pressure Potential = +1 barSolute Potential = -4 bars

Which way does the water move?

Solute difference

Pipe #1

Pressure Potential = +1 barSolute Potential = -2 bars

Membranepasses water only

Pipe #2

Pressure Potential = +1 barSolute Potential = -4 bars

Water (only) moves from higher to lower potential.

Pressure and solute differences--I

Pipe #1

Pressure Potential = +1 barSolute Potential = -1 bars

Membranepasses water only

Pipe #2

Pressure Potential = +3 barsSolute Potential = -4 bars

Which way does the water move?

Pressure and solute differences--I

Pipe #1

Pressure Potential = +1 barSolute Potential = -1 bars

Membranepasses water only

Pipe #2

Pressure Potential = +3 barsSolute Potential = -4 bars

Water (only) moves from higher to lower water potential.

Pressure and solute differences--II

Pipe #1

Pressure Potential = -4 bars Solute Potential = -1 bars

Membranepasses water only

Pipe #2

Pressure Potential = +2 barsSolute Potential = -8 bars

Which way does the water move?

Pressure and solute differences--II

Pipe #1

Pressure Potential = -4 barsSolute Potential = -1 bar

Membranepasses water only

Pipe #2

Pressure Potential = +2 barsSolute Potential = -8 bars

Water (only) moves from higher to lower water potential.

Pressure and solute differences--III

Pipe #1

Pressure Potential = -4 bars Solute Potential = -1 bars

Membranepasses water only

Pipe #2

Pressure Potential = +2 barsSolute Potential = -7 bars

Which way does the water move?

Pressure and solute differences--III

Pipe #1

Pressure Potential = -4 barsSolute Potential = -1 bar

Membranepasses water only

Pipe #2

Pressure Potential = +2 barsSolute Potential = -7 bars

No NET water movement: Pipes at equilibrium for water potential.