Nater potential is the potential energy of water relative to pure free water in reference conditions. It quantifies the tendency of water to move from one area to another due to osmosis, gravity, mechanical pressure or matrix effects including surface tension. Water potential is measured in units of pressure and is commonly represented by the Greek letter 141’ (Psi).
Typically, pure water at standard temperature and pressure is defined as having a water potential of 0. The addition of solutes to water lowers its potential just as increase in pressure increases its potential. Seawater typically has negative water potentials relative to the pure water reference. If there is no restriction on flow, water molecules will proceed from the locus of pure water to the more negative water potential of the solution. Water potential of a cell is affected by both solute and pressure potential. The relationship between them is as follows
Ψw = ΨB + Ψp
