Question

Explain why pure water has maximum water potential.

Answer 1

The measure of the potential energy in water, as well as the difference between the potential in a given water sample and pure water, is known as water potential. Water potential is determined by solute concentration and pressure.

Complete step by step answer:
Water potential has the tendency of water to flow from one part to the other during various cellular processes. It is denoted by the Greek letter Psi. At standard temperature and pressure, the water potential of pure water is always taken as zero. This is explained by the kinetic energy possessed by water molecules. The movement of its molecules is rapid and constant when water is in liquid form. Also, pure water has the highest concentration of water molecules. Therefore, it has the highest water potential. The water potential of pure water decreases when some solute is dissolved in water. The osmotic potential of pure water is defined to be zero because there is no solute. But the water potential of pure water in an open container is zero due to the reason that there is no solute and the pressure in the container is zero. Water potential is given by taking osmotic (or solute) potential and pressure potential and is determined by the formula:
Water potential = Osmotic Potential + Pressure Potential
$\psi ={{\psi }_{S}}+{{\psi }_{P}}$
${{\psi }_{P}}=$ the solute or osmotic potential
${{\psi }_{S}}=$ the pressure potential

Note:
- If a plant cell is placed into water, obviously water will enter the cell because water features a higher water potential than the plant cell itself. However, when the plant cell’s central vacuole fills with water, then it'll keep off the water surrounding the cell. The plant cell doesn’t burst thanks to this pressure because it's a cell membrane. When the pressure exerted outward on the water surrounding the plant cell is adequate to the osmotic potential of the answer within the cell, the water potential of the cell is going to be adequate to zero. The water potential of the plant cell also will be adequate to the water surrounding it, and there'll be no net movement of water molecules.
Water Potential Principles:
- Addition of solute decreases water potential
- Addition of pressure increases water potential
- A hypertonic solution features a lower water potential
- A hypotonic solution features a higher water potential