Differences between Differential Pressure Deficit (DPD) and Water Potential!
Differential Pressure Deficit (DPD):
1. It is an old term that was coined by Meyer (1938). It is equivalent to water potential.
2. It has positive value, e.g., 5 atm.
3. DPD is the reduction in diffusion pressure of solvent in a system over its pure state.
4. Water is absorbed by a system having higher DPD from another system with lower DPD.
5. DPD = OP – TP where all terms are with positive value.
6. Matrix pressure or imbibition force is not considered.
Water Potential:
1. Coined by Slatyer and Taylor (1960) and is equivalent to DPD.
2. It has negative value, e.g., – 5 atm.
3. It is reduction in free energy of solvent in a system over its pure state.
4. Water is absorbed by a system with lower water potential from another system with higher water potential.
5. Ψw = Ψs + Ψp where Ψs has a negative value while Ψp has a positive value.
6. Matrix potential or Ψm is considered wherever it is appreciable.