Explanation

Water potential is the difference in the free energy or chemical potential per unit molal volume of water in a system and that of pure water at the same temperature and pressure. It is represented by greek letter $\Psi$ (psi) or more accurately $\Psi_{w}$ Water potential or $\Psi_{w}$ is the sum total of $\Psi_{s}\ and\ \Psi_{p}$. $\Psi_{w} = \Psi_{s} + \Psi_{p}$ Where, $\Psi_{s} \rightarrow$ solute potential $\Psi_{p} \rightarrow$ pressure potential