Question

If DPD represents diffusion pressure deficit, OP is the osmotic pressure and TP is the turgor pressure, then which of the following equations is correct ?

• A. DPD = OP = TP
• B. DPD = OP + TP
• C. DPD = OP-TP
• D. DPD = OP

Answer 1

Answer: (C)

The reduction in the diffusion pressure of water in a solution over its pure state is called diffusion pressure deficit or $DPD$. Diffusion pressure deficit is also called suction pressure. Its value is equal to the osmotic pressure or potential $(OP)$ (positive value taken in bars or atm) of the solution in a cell or system minus the wall pressure $(WP)$ ($=$ turgor pressure, $TP$) which opposes the entry of water into it provided the external water is pure. $DPD=OP-WP(=TP)$
Water is absorbed by a system having higher $DPD$ from another system with lower $DPD$.