Question

When a cell is plasmolyzed, it becomes
A. Flaccid and its TP becomes zero
B. Turgid and its TP becomes zero
C. Turgid and TP becomes equal to OP
D. Flaccid and DPD becomes zero

Answer 1

Hint: When water enters the cell, it becomes turgid and when water is lost from the cell, it becomes plasmolyzed. The loss of water occurs along a concentration gradient by the process called osmosis.

Complete answer:
A plant cell is surrounded by the cell membrane and a cell wall, from which the cell membrane is selectively permeable to various substances and the cell wall is freely permeable to water and substances in solution. A hypertonic solution is the one in which the concentration of solute is high as compared to the other solution. An isotonic solution is the one in which the concentration of the solute is the same as that of the other comparable solution. A hypotonic solution is the one in which the concentration of the solute is less than that of the other solution that means the solution present in the system is dilute or has more solvent molecules. When there is a concentration gradient present between the cell and the surrounding medium, movement of water molecules or solvent molecules takes place along the concentration gradient. This movement of water molecules is called osmosis where the cell membrane acts as a semipermeable membrane. Since it is passive transport and takes place along the concentration gradient, no consumption of ATP takes place. When a cell is placed in a hypertonic solution, water moves out of the cell resulting in plasmolysis of the cell in which the cell membrane of the plant cell shrinks away from its cell wall.
When a cell is placed in an isotonic solution, the osmotic pressure of the protoplasm is balanced with the osmotic pressure of the surrounding fluid, then there is no net flow of water molecules in and out of the cell. Hence, the cell is in equilibrium with the fluid and the cell is said to be flaccid.
When a cell is placed in a hypotonic solution, water enters the cell resulting in the pressure building up on the walls of the cells thus making the cell turgid. This pressure exerted on the cell wall is called pressure potential.
In the plasmolyzed condition of the cell, turgor pressure (TP) becomes zero. The pressure that pushes the plasma membrane against the cell wall is called turgor pressure which is responsible for enlargement and extension growth of cells.
Hence, the correct answer is option A.

Note: In a plant cell, vacuole occupies around 90% of the volume of the cell. During plasmolysis, water is first lost from the cytoplasm and then from the vacuole. The vacuolar sap present in the vacuole contributes to the solute potential of the cell.