Question

What occupies the space between the cell wall and a shrunken protoplast and the plasmolyst cell?

Answer 1

Cell walls are usually semi-permeable, if not fully permeable i.e. they allow the passage of water and certain solutes. In a plasmolysed cell, the protoplast loses water due to exosmosis and thus shrinks away from the cell wall. Thus, the space between the protoplast and the cell wall would consist of a solution (water and certain solutes) present in the extracellular region of the cell.