Question

Differentiate between osmotic potential and matric potential.

Answer 1

Hint: Between two regions, if a difference in water potential exists, spontaneous movement of water will take place and the direction of flow of water will be energetically downhill, that is, from the region of higher potential to the region lower water potential. For a solution like the contents of a cell, water potential is determined by internal factors like: Matric potential, Solute potential or osmotic potential and Pressure potential.

Complete answer:

MATRIC POTENTIAL	OSMOTIC POTENTIAL
1. It is the reduction in free energy of water as a result of the formation of a thin immobile surface layer of the water molecules.	1. It is the reduction in the free energy of water due to the decrease in the number of the water molecules per molal volume.
2. Matric potential is caused by the colloidal particles adsorbent.	2. Osmotic potential is caused by the presence of the solute particles.
3. It is essential for seed germination: growth of the developing fruits and early seedling growth.	3. It is an important factor in the water relation of the plant seeds.
4. Matric potentials are always negative to zero.	4. Osmotic potentials are always negative values.

Additional information:
Osmotic potential is also known as solute potential. Osmotic potential is the amount by which water potential is decreased as a result of the presence of solute. Osmotic potentials are always negative values. Pure water at a water potential equal to zero is considered as the reference standard. Therefore, a reduction from this standard value gives a negative number.
Matric potential is the amount of water bound to the matrix of a plant via hydrogen bonds and is always negative to zero. In a dry system, in a dry seed it can be as low as 2 MPa, or as high as zero in a water saturated system. Every plant cell has a cellulosic cell wall that is hydrophilic and provides a matrix for water adhesion; hence it is named as matric potential. Matric potential is similar to the solute potential because the hydrogen bonds remove the energy from the total system. However, in case of the solute potential, the other components are hydrophilic solute molecules, soluble whereas in Matric potential, the other components are insoluble, hydrophilic molecules of the plant cell wall.

Note: Another factor affecting water potential is the pressure potential and it is a hydrostatic pressure. This is a pressure that develops in the osmotic system due to the osmotic exit or entry of water from it. Pressure potential increases the water potential in a system.