Solute Potential Ψ s

The effect of dissolving solute molecules in pure water is to reduce the concentration of water molecules and hence to lower the water potential. All solutes therefore have lower water potentials than pure water. The amount of this lowering is known as the solute potential. In other words, solute potential is a measure of the change in water potential of a system due to the presence of solute molecules. Ψ s is always negative. The more solute molecules present, the lower (more negative) is Ψ s.

Solute potential (Ψs) is a measure of the effect of solutes on the water potential of a solution. It is a component of the overall water potential (Ψw) and is defined as the pressure that must be applied to a solution to prevent the inward flow of water across a semipermeable membrane. The solute potential of a solution is determined by the concentration of dissolved solutes in the solution and is usually negative, meaning that it decreases the overall water potential of the solution. Solute potential is an important concept in plant physiology, as it plays a role in the movement of water and nutrients between plant cells and the environment.