Briefly describe water potential. What are the factors affecting it?

(N/A) Water potential quantifies the tendency of water to move from one area to another during various cellular processes such as diffusion and osmosis. It is denoted by the Greek letter Psi $(\Psi)$ and is expressed in pressure units like Pascals $(Pa)$. The water potential of pure water at standard temperature and pressure is defined as zero.
Water potential $(\Psi_{W})$ is determined by the sum of solute potential $(\Psi_{S})$ and pressure potential $(\Psi_{P})$:
$\Psi_{W} = \Psi_{S} + \Psi_{P}$
Factors affecting water potential:
$1$. Solute potential $(\Psi_{S})$: When a solute is dissolved in pure water,the concentration of free water molecules decreases,reducing the water potential. Solute potential is always negative.
$2$. Pressure potential $(\Psi_{P})$: Applying pressure greater than atmospheric pressure increases the water potential. It is usually positive,though negative pressure (tension) can occur in the xylem,which is crucial for the ascent of sap.