Partial plasmolysis creates a gap filled by external solution

Steps:

• Plasmolysis occurs when a plant cell loses water in a hypertonic external solution, causing the cytoplasm to shrink away from the cell wall.
• In partial plasmolysis, the protoplast pulls away incompletely, forming a gap labeled Z between the cell wall and membrane.
• This gap allows the external solution to occupy the space as the cell dehydrates.
• Solution Y is the external hypertonic medium surrounding the cell, entering Z during water loss.

Why C is correct:

• By osmosis, water exits the cell into hypertonic solution Y, and Y fills the resulting gap Z, as the cell wall is permeable to solutes.

Why the others are wrong:

• A: Air cannot occupy Z in an aqueous cell environment; the setup involves liquid solutions.
• B: Solution X is the internal cell sap, retained within the shrunken protoplast, not the external gap.
• D: Water is hypotonic and would prevent plasmolysis by entering the cell, not filling Z.

Final answer: C