Question

Read the given statements that refer to different stages of plasmolysis. Select the correct option regarding them. (i) First stage of plasmolysis, when osmotic concentration of cell sap is just equivalent to that of external solution. (ii) Protoplast withdraws itself from corners of the cell wall. (iii) Protoplast gets detached from the cell wall and attains a spherical shape.

• A. a
• B. b
• C. c
• D. d

Answer 1

The Correct Option is B

Shrinkage of the protoplast of a cell from its cell wall under the influence of a hypertonic solution is called plasmolysis. Hypertonic solution causes exosmosis or withdrawal of water from cytoplasm and then the central vacuole of cell. The size of cytoplasm as well as central vacuole and hence protoplast becomes reduced. The pressure on the wall is simultaneously reduced and the elastic wall contracts causing a reduction in cell size. This is first stage of plasmolysis called limiting plasmolysis. At limiting plasmolysis, the pressure potential $\left(\Psi_{p}\right)$ is zero and the osmotic concentration of cell interior is just equivalent to that of external solution (isotonic). The cell is called flaccid. The extra hypertonic external solution continues to withdraw water from the central vacuole by exosmosis. Initially the protoplast withdraws itself from the corners. This stage is known as incipient plasmolysis. Due to continued exosmosis, protoplast shrinks further and withdraws from the cell wall except one or a few points. It is known as evident plasmolysis.