Question

Plant cell kept in strong saline solution will
A) Remain unchanged
B) Decrease in size
C) Increase in size
D) Burst out

Answer 1

Hint: Plasmolysis is the shrinkage of a plant cell's cytoplasm in reaction to water diffusion out of the cell and into a high-salt solution. The cell membrane pushes away from the cell wall during plasmolysis. Because of the stiff cell wall, this does not happen at low salt concentrations.

Complete answer:
The water potential of two solutions separated by a semipermeable cell membrane is measured by tonicity, which is a measure of the effective osmotic pressure gradient. To put it another way, tonicity is the concentration of dissolved solutes in a solution that determines the direction and amount of diffusion.

On the basis of tonicity it can be divided into three
- Isotonic Solution: Both sides of the cell membrane have the same relative concentrations of water molecules and solute. As a result, water molecules do not move in a net motion.
- Hypotonic solution: In this case, the solute concentration outside the cell is lower than the solute concentration inside the cell. Endosmosis occurs when water enters the cell, causing the cell to become turgid.
- Hypertonic solution: In this case, the solute concentration outside the cell is higher than the solute concentration inside the cell. As a result, exosmosis occurs, in which water moves out of the cell and the cell becomes flaccid.

Because the saline solution is hypertonic in comparison to the cell, a plant cell kept in a strong saline solution shrinks. Because it is a hypertonic solution, it contains fewer solvent molecules than the fluid inside the cell. Exosmosis is the process by which solvent molecules are pushed outside the cell from a region of higher concentration to a region of lower concentration. Flaccidity develops in the cell.

Therefore the correct answer is option ‘B’.

Note: Tonicity refers to an extracellular solution's ability to cause water to migrate into or out of a cell via osmosis. Tonicity differs from osmolarity in that it considers both relative solute concentrations and the permeability of the cell membrane to those solutes.