The Effect of Salt on Plant Cells
Salt and Plant Cells teacher's guide
Osmosis Demonstration worksheet
Salting an eggplant demonstrates the effect of salt on plant cells.
- A large eggplant
Distribute the worksheets or investigation booklets for students to use to draw their predictions of what will happen when the eggplant is salted. (Students will also use the investigation booklet for the salt and ecosystem case studies that follow.)
Demonstration: Salting the eggplant
Key Idea: Salt pulls water out of cells killing them.
In their Investigation Booklet or worksheet, ask students to draw their predictions of what will happen when you place salt on the eggplant.
- Slice a large eggplant in half longitudinally
- Cover the eggplant with generous amounts of table salt.
- Watch how the salt draws the water out of the cells (osmosis). The eggplant will get very wet.
NOTE: It can take 15 minutes for the water to leave the eggplant. You may want to set up this demonstration at the beginning of the period and return to it after completing the next steps in the lesson.
Question: Where did all the water come from?
Answer: The water is pulled out of the cells by the process of osmosis (See Teacher Tip for another suggested demonstration about osmosis).
Question: What happens to the eggplant without all of that water?
Answer: If the eggplant was still growing, its cells would not have the necessary water to perform important life functions and would die.
Question: How do you feel when you eat potato chips? Are you thirsty? What do you think is happening to your cells? Answer: The water is diffusing via osmosis out of the cells, decreasing the quantity of water in their cells and causing them to be dehydrated. That is why after eating a bag of potato chips, you feel thirsty.
Question: Using what happened to the salted eggplant, develop an explanation for what happens to a person’s cells when a person drinks seawater?
Answer: A person’s cells would also lose water that they need for normal life functions, which would disrupt homeostasis (a stable internal environment) causing that person’s cells and eventually that person to die!
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