Introductory Crop Physiology

SOLUTE POTENTIAL

It is also known as osmotic potential. The amount of solute present in water is called as solute potential. It can also be defined as the amount by which the water potential is reduced as a result of the presence of solute. It has got a negative value.
In 1887, Vant Hoff, J. H., discovered an empirical relationship that allows calculation of an approximate osmotic potential form the molal concentration of a solution. He ploted osmotic potential from direct osmometer reading as function of molal concentration and obtained the following relationship which has the exact form as the law for perfect gases.
? = -miRT

where, ? = osmotic potential
m = molality of solution
i = a constant that accounts for ionization of solution.
R = Gas constant (8.3144621 J K?1 mol?1)
T = Absolute temperature
(K) = oC + 273
If m, i and T is known for any solution,

Then osmotic potential can be easily calculated. Osmotic potential for a complex solution such as cell sap is the sum of all osmotic potential caused by all solutes, it is expressed as osmolality.