Question

Given diagram illustrates the changes that occur when a plant cell takes up water. Identify L, M and N and select the incorrect statement regarding the given diagram

• A. N is the diffusion pressure deficit which becomes zero when L and M are equal in magnitude
• B. In a flaccid cell, value of N becomes equal to that of L
• C. M represents osmotic pressure, which increases when a flaccid cell takes up water
• D. L represents solute potential, which decreases with the increase in turgidity of the cell

Answer 1

Answer: (C)

Given diagram illustrates the changes that occur when a flaccid plant cell takes up water. $L$ represents osmotic pressure $(OP)$ or solute potential $\left(\Psi_{s}\right)$, $M$ represents turgor pressure $(TP)$ or pressure potential $\left(\Psi_{p}\right)$ and $N$ represents diffusion pressure deficit $(DPD)$ or water potential $\left(\Psi_{w}\right)$.
In a flaccid cell, $TP$ is zero, therefore, $DPD = OP - O = OP$. When a flaccid cell is placed in water, it takes up water due to endosmosis, $OP$ of the cell starts decreasing while $TP$ starts increasing. In fully turgid condition, $OP$ and $TP$ become equal so that $DPD$ becomes zero.