Question

The difference between osmotic pressure and turgor pressure is
A. Diffusion pressure Deficit (DPD)
B. Transpiration pull
C. Osmotic potential
D. Solute potential

Answer 1

Hint: The difference between osmotic pressure and turgor pressure results in the diffusion pressure deficit. Mathematically, DPD= Osmotic pressure (OP) – Turgor pressure (TP). DPD is the pressure difference between pure water and solution.

Complete answer:
Option A- Diffusion pressure Deficit (DPD)
The diffusion pressure deficit (DPD) was coined by B.S Meyer in 1938. Initially, DPD was described as suction pressure by Renner in 1915. It refers to a reduction in the diffusion pressure of water in solution or cell over its pure state. This is due to the presence of solutes in it and forces opposing diffusion.

Option B- Transpiration pull
Transpiration pull, also known as suction force, is the force which aids in drawing the water upward from roots to leaves. In leaves, some fraction of water is used for photosynthesis and excess water is released into the atmosphere through openings known as stomata.

Option C- Osmotic potential
Osmotic potential or Water potential is the potential energy of water per unit volume relative to pure water in reference conditions. It quantifies the tendency of water to move from one area to another. This is due to osmosis, gravity, mechanical pressure, and matrix effects such as capillary action.

Option D- Solute potential
Solute potential refers to the component of water potential that is due to the presence of solute molecules. It constantly has a negative value as solutes lower the water potential of the system.

Hence, option A- Diffusion pressure Deficit (DPD), is correct.

Note: Osmotic pressure refers to the minimum pressure that needs to be applied on the solution to prevent the inward flow of its pure solvent across a semipermeable membrane whereas turgor pressure refers to the pressure inside the cell pushes the plasma membrane against the cell wall of the plant cell.