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Isotonic Point Lab Report

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The four different plant cells had different isotonic points and, therefore, proved that the internal solute concentration of plants in a different environment are different. To elaborate further, the isotonic point is defined in this lab as having about 50% plasmolyzed and 50% unplasmolyzed cells in a specific species. In terms of salt concentration, a higher isotonic point indicates that the solute concentration inside the cell is higher than outside the cell. For example, plant cells with an isotonic point at 4% salt concentration have more solutes inside the cell compared to a 1% salt concentration because they maintain their turgor pressure at higher concentrations. The salt concentration will always refer to the outside environment of the cell unless otherwise specified. The Onion cells …show more content…

Overall, the plant cells did not have an isotonic point higher than 4%. The difference in isotonic point between plant cells of different environment provides strong evidence for the hypothesis. The freshwater Elodea plant cells had an isotonic point of 1% while the saltwater Ulva plant cells had an isotonic point at about 4% supporting the idea that saltwater plants evolved to endure higher salt concentrations and have a higher isotonic point. Both the Onion cells and Fern Prothallia cells have isotonic points at 3% salt concentration suggesting that terrestrial plant cells have an isotonic point at about 3% salt concentration. Compared to sea water (salt concentration at 3%) the freshwater plants have lower solute concentration inside their cells, hence the plasmolysis of cells at lower salt concentrations, while saltwater plant cells have higher solute concentration, hence the plasmolysis of cells at higher salt concentrations. This evidence suggests that the plants evolving in environments with higher salt concentrations evolved to endure much higher salt concentrations from their

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