What causes a plant cell to be turgid?

What causes a plant cell to be turgid? HINT: Refer to the textbook Ch. 5, p. 76, 5.5 “Water balance between cells and their surroundings is crucial to organisms.” The information about marine plants is misleading.
Explain what happens to the cells of the Elodea leaf S1 in distilled water AND to the cells of leaf S2 in 20% NaCl solution. HINT: Include the terms “hypotonic” and “hypertonic” in your responses.