Osmosis and Water Potential in Plant Cells

Steps:

• Adding NaCl increases solute concentration in the culture solution.
• Higher solute concentration lowers water potential, making it more negative (ψ = ψ_s + ψ_p, where ψ_s decreases).
• Freshwater plant cells have higher (less negative) water potential than the solution.
• Water moves out of cells by osmosis, causing cytoplasm to shrink and plasmolysis after 5 minutes.

Why C is correct:

• Adding solutes decreases solution water potential (more negative per water potential formula), driving water out of cells and causing plasmolysis (cytoplasm pulls away from cell wall).

Why the others are wrong:

• A: Water potential becomes more negative, not less.
• B: Water potential becomes more negative; cells lose turgor, not gain it.
• D: Cells lose water and become plasmolysed, not turgid.

Final answer: C