Water potential of a solution is :

Water molecules possess kinetic energy. The greater the concentration of water in a system, the greater is its kinetic energy or ‘water potential’. By convention, the water potential of pure water at standard temperatures, which is not under any pressure, is taken to be zero. If some solute is dissolved in pure water, the solution has fewer free water molecules and the concentration (free energy) of water decreases, reducing its water potential. Therefore, water potential of a solution is negative.