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Biology LibreTexts

Exercise 2: Observation of Osmosis in a plant cell

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  • Observation of Osmosis in a plant cell

    Plants have cell walls that can prevent lysis if too much water flows into the cell. Plant cytoplasm tends to be hypertonic to the outside environment, which results in an inflow of water and a high amount of pressure (turgor pressure) inside the cell. When a plant is placed into a hypertonic environment, the water will leave the cell. This causes the cell to shrink and detaches the plasma membrane from the cell wall (plasmolysis). Turgor pressure can hold plants upright, while plasmolysis can cause plants to wilt.


    Observe the two Elodea leaves under the microscope. One slide is a leaf in isotonic solution: you should be able to identify the chloroplasts and an empty space in the middle of the cells which is the vacuole. The next leaf has been soaked in a salt water solution; compare the cells to the first slide.


    1. What is the difference between a hypertonic solution and a hypotonic solution?


    2. What will happen to plant cells that are placed in a hypertonic solution?


    3. What will happen to animal cells placed in hypotonic solution? Why should this be different from plant cells?


    4. Why are dehydrated patients given saline intravenously instead of water?