Why does pure water have maximum water potential?
Following are the reasons for the maximum water potential of pure water: i) Water molecules have a constant motion, hence, have kinetic energy in both liquid and gaseous phases. ii) The kinetic energy of the water potential is directly proportional to the concentration of water in a system. iii) Pure water has the greatest water potential. iv) When two water-containing systems are in contacts such as soil and air or cell and the solution, then there occurs the random movement of water molecules from high energy systems to low energy systems. The water molecules move from a system containing high water potential water to a low water potential system at equilibrium. v) Water potential is expressed in the units of pressure i.e. Pascal and represented as Psi or Ψ. At a particular temperature and pressure, the water potential of pure water is equal to zero. vi) The water potential of any solution is lower than that of pure water because the dissolution of a solute with pure water lowers its concentration and thereby lowers the water potential.
