Question

A cell with $DPD=5$ is surrounded by A, B, C, and D cells having O.P. and T.P. 5 and 4, 7 and 5, 3 and 2, zero and zero respectively. From which cell will the water withdraw faster?
I. D
II. C
III. B
IV. A

Answer 1

Hint: To calculate DPD for cells A, B, C and, D. The DPD of a cell can be calculated as the difference between O.P. and the T.P. In addition, the more the DPD of a cell the more it is thirsty for water and less it will hold it.

Formula used:
The DPD of a cell can be calculated by the formula $DPD=O.P-T.P. $, where $DPD$ stands for Diffusion pressure deficit, $O.P.$ stands for Osmotic pressure and $T.P.$ stands for Turgor pressure.

Step by step answer:
DPD stands for diffusion pressure deficit that means thirst of the cell for water. The osmotic pressure of the cell or $O.P. $ is the net movement of the solvent molecules from the semi-permeable plasma membrane to a region of higher solute concentration. And the Turgor pressure or $T.P. $ of the cell is termed as the hydrostatic pressure of cells. It is the force that pushes the plasma membrane towards the cell wall.
Now, let’s calculate DPD for each cell.
For, the first cell, the O.P., and T.P. are 5 and 4 respectively. The formula used is $DPD=O.P.-T.P. $ Substituting 5 for $O.P.$ and 4 for T.P, we get,
Thus, $5-4=1$
So, 1 is the DPD for cell A.
For, the second cell, the O.P., and T.P. are 7 and 5 respectively. The formula used is $DPD=O.P.-T.P. $ Substituting 7 for $O.P.$ and 5 for T.P, we get,
Thus, $7-5=2$
So, 2 is the DPD for cell B.
For, the third cell, the O.P., and T.P. are 3 and 2 respectively. The formula used is $DPD=O.P.-T.P. $ Substituting 3 for $O.P.$ and 2 for T.P, we get,
Thus, $3-2=1$
So, 1 is the DPD for cell C.
For, the last cell, the O.P., and T.P. are 0 and 0 respectively. The formula used is $DPD=O.P.-T.P. $ Substituting 0 for $O.P.$ and 0 for T.P, we get,
Thus, $0-0=0$
So, 0 is the DPD for cell D.
Now, the DPD for cells A, B, C and, D are 1, 2, 1 and, 0 respectively.
To obtain the lowest value we can arrange it in ascending order.
 $0<1<1<2$.
Thus, the right answer is option A. Cell D has the lowest DPD value and will withdraw water faster as compared to other cells.

Note: The DPD of a cell is indicative of its swelling. A fully turgid cell will have a DPD of zero and a plasmolyzed cell will have maximum DPD value. The ascent of sap in plants using DPD values for cells involved.