Question

What occupies the space between the cell wall and the shrunken protoplast in the plasmolyzed cell?

Answer 1

We are familiar that Plasmolysis is one type of osmosis i.e. movement of liquid from higher concentration to lower concentration through a semipermeable membrane. Plasmolysis is shrinkage of the protoplast of the cell due to the loss of water. De-plasmolysis is swelling of protoplast when kept in a hypotonic solution. There are three types of solutions: Hypertonic, Hypotonic and Isotonic.

Complete answer:
Hypertonic solution: The external solution is more concentrated than the cytoplasm. Hypotonic solution: The external solution is more dilute than the cytoplasm. Isotonic solution: Both the solutions have the same concentration.
Plasmolysis occurs when the cell is placed in a hypertonic solution as it is a concentrated solution. A cell is said to be plasmolyzed when the water content moves out of the cell and the cell membrane shrinks away from the cell wall.
As we know that water moves from higher potential to the lower potential thus, in case of plasmolysis the water moves from the cell to the solution.
As this occurs initially the cytoplasm within the cell starts to shrink and this is known as incipient plasmolysis.
The ex-osmosis continues and the protoplasm becomes a contracted mass and gets arranged into a corner and the space between the cell wall and shrunken protoplast becomes filled with the outer solution i.e. hypertonic solution. This is known as total plasmolysis.
The process of plasmolysis is reversed if the cell is kept in a hypotonic solution, the cell will swell and if it continues then it may get ruptured.

Hence, the space between the cell wall and the shrunken protoplast in the plasmolyzed cell is occupied by the outer solution i.e. Hypertonic Solution.

Note: Plasma membrane is selectively permeable so it is able to control the movement of substances in and out. When the cell is kept in a hypotonic solution, the cell swells and there is an increase in turgor pressure. When the cell is kept in a hypertonic solution cell shrinks. When the cell is kept in an isotonic solution there is no change and such a condition of the cell is known as a flaccid cell.