How does increase in pressure increase the water potential ? 

The difference between the free energy of water molecules in pure water and the energy of water in any other system is termed water potential. Pressure potential is one of the component of water potential.

 

Pressure potential increases as water enters a cell. As water passes through the cell wall and cell membrane, it increases the total amount of water present inside the cell, which exerts an outward pressure . By creating this pressure, the plant can maintain turgor, which allows the plant to keep its rigidity.