Water Potential and Its Components - Practice Questions & MCQ

• The concept of water potential was given by Slatyer and Taylor in 1960.
• The potential energy of water is called water potential. e.g., water is stored behind a dam.
• The term ‘water potential’ is used to describe the tendency of the water molecules to move from one place to another.
• Water moves from the region of high water potential to low water potential.
• Water potential of pure water is maximum which is taken as zero.
• Water potential of solutions is always less than zero, that is, they have negative water potential.
• Water potential is denoted by ψ_w
• It is measured in Mega Pascal (MPa).

Components of Water Potential:

• Pressure Potential (ψ_P): It is the hydrostatic pressure of a solution. It is taken as zero at atmospheric pressure. It is generally positive but negative pressure also builds up in the xylem vessels. When pressure is applied externally, water potential becomes positive.
• Osmotic Potential or Solute Potential (ψ_s): It is the potential developed due to the addition of the solute. 
• Gravity: It is generally taken negligible.
• Matrix Potential: When the hydrating colloids adsorb water on their surfaces, free energy is released. This is called matrix potential. It is always negative. It is also taken as negligible.
• Therefore, the water potential can be given as:
  • Water Potential = Pressure Potential + SolutePotential