Define and explain water potential.

Water potential is defined as the chemical potential (free energy) of water.
* Water potential is denoted by the Greek symbol Psi or $\mathrm{\psi }$.
* It is expressed in pressure units such as pascals (Pa).
* The water potential of pure water at standard temperatures, and pressure is taken to be zero.
* Water will move from the region with higher water potential to the region with low water potential.
* Solute potential (${\mathrm{\psi }}_{\mathrm{S}}$) and Pressure potential (${\mathrm{\psi }}_{\mathrm{P}}$) are the two main components that determine water potential.
* ${\mathrm{\psi }}_{\mathrm{w}}={\mathrm{\psi }}_{\mathrm{s}}+{\mathrm{\psi }}_{\mathrm{p}}$.