If some solute is dissolved in solvent, its diffusion pressure decreases.
When a cell is fully turgid, its OP is equal to TP and DPD is zero.
The term diffusion pressure deficit (DPD) was coined by B.S.
[3] Originally DPD was described as suction pressure by German botanist Otto Renner in 1915.
The suction pressure, along with the suction temperature the wet bulb temperature of the discharge air are used to determine the correct refrigerant charge in a system.