Salinization Lab
Salinization Lab
Purpose:
To involve students in a real world scientific investigation in which they design an experiment to determine how
the concentration of salt in water affects the germination rate of seeds.
Background information:
Salt buildup is a potential problem on almost all of the irrigated farmland in the United States. Much of the
world's unused land is in arid or semiarid regions where irrigation would be necessary to grow crops. A small
amount of salt in the soil will not affect the germination and growth of crops. Eventually, however, if salt
concentrations increase, negative impacts occur. Eventually salt concentrations will affect the germination of
seeds. Farmers need to know the relationship between the salt concentration and the percent of seeds that will
germinate.
Salt kills germinating seedlings by removing the water from their cells. There are several salts that are
responsible but this lab will involve only one, sodium chloride (NaCl). From your results you can assume that
other salt concentrations would also affect germination rates. NaCl has a solubility of 35.7 g per 100 mL of
water. Ocean water has a concentration of 3.5% which is 3.5 g/100 mL of water. Freshwater has a concentration
of 0.005 % salt which is 0.005 g/100 mL of water.
Procedure:
1. After reading, the first part of the lab, the "problem" has been identified. From this you should be able to
formulate a hypothesis.
2. You must now identify your independent and dependent variables. To do this, make a question - What is the
effect of the independent variable on the dependent variable? This will tell you not only the variables but also
which variable to put on each axis of the graph. [Remember, the x-axis is the horizontal axis and is the
independent variable. The y-axis is the vertical axis and is the dependent variable.]
3. Decide what you will use as a control. You will also need to identify the constants in the experiment.
4. Be sure to keep accurate data tables and check on your experiment daily. When the experiment is completed,
turn in a lab report including graphs. Be sure to do an analysis and a conclusion.
Materials:
Zip-loc bags, paper towels
Serial dilutions of NaCl concentrations - 0, 0.25, 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0 grams/100 mL H2O
Distilled water
Graduated cylinders, 25 mL
Balances, electronic
Volumetric flasks, 100 mL
Seeds, radish, squash or wheat
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Salinization Lab
Procedure:
1. Using a balance, weigh out the following amounts of salt: 0, 0.25, 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0 grams
2. Measure 100 mL of water for each amount of salt used.
3. Mix the water with the salt and stir until completely dissolved.
4. Fold paper towels into squares;
5. Wet slightly the paper towel to keep the seeds from rolling of the towel, and place 10 radish/squash seeds on
the towel.
6. Carefully fold the towel in half and place it inside the Zip-loc bag.
7. Using a graduated cylinder, measure 20 mL of the desired salt solution and add to the labeled plastic bag.
8. Remove excess air and seal the bag to prevent evaporation.
9. Complete steps 5-8 until all salt concentrations have been used. Record all data in the data table
10. Place the bags in a secure location (wall cabinet or drawer) until the next class period.
11. Check the status of your seeds during the next two class periods, recording your information in the data table.
Label
Number of
Seeds used
Control
0.25
0.50
0.75
1.00
1.50
2.00
2.50
3.00
10
10
10
10
10
10
10
10
10
Number of
Amount of
Number of
Concentration
seeds
Salt
seeds with no
of salt solution
germinated
solution, mL
growth
20
20
20
20
20
20
20
20
20
%
germination
0
0.25
0.50
0.75
1.00
1.50
2.00
2.50
3.00
Graphs: From your data table you should be able to draw two graphs.
1. Construct a line graph on which you compare the % of salt solution on the x - axis with the number of seeds
which germinated on the y-axis. Be sure and give your graph a title and label the axes.
2. Construct a bar graph on which you compare the percentage of salt solution on the x-axis with the % of seeds
that germinated on the y-axis.
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Salinization Lab
Analysis:
1. Does there seem to be a relationship between the number of seeds which germinated and the concentration of
the salt water? If so, what is that relationship?
2. Did your experiment support your hypothesis?
3. Can you think of any errors that might have occurred that would invalidate your experiment? If so what were
they and how might they be corrected?
4. Explain why increasing levels of salt concentrations affect seed growth and why irrigation seems to be the
main cause of this.
5. Do you think all seeds would be affected in similar ways as the ones you used?
6. When soil becomes too salty, what are some methods of remediation?
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