Salinization Lab
NAME______________________
Purpose:
To conduct an experiment to determine how the concentration of salt in water affects the germination
rate of seeds by measuring carbon dioxide gas production from cellular respiration.
Background Information:
Salt buildup is a potential problem on irrigated farmland
in
the United States. Much of the world's unused land is in arid 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. However, if salt concentrations increase, negative impacts occur. Salt concentrations 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 involved
in this process. This lab will use sodium chloride (NaCl) as a model. 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.
Materials:
plastic bags paper towels
Distilled water 25 mL graduated cylinder scoopula stir rod
Electronic Balance
weigh boat 100 mL Flask Alaska Pea Seeds CO2 Probes Go Links
NaCl concentrations - 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 grams/100 mL
Procedures:
Computer + Probeware Set Up:
1. Begin by setting up probe and LoggerPro to allow the probeware to calibrate.
2. Connect the GoLink to the computer and the gas probe to the GoLink. Rest probe on countertop.
3. Under Applications, Open LoggerPro.
4. Click on “File” then click on “Open” – see Experiments folder.
5. Click on “Advanced Biology w/Vernier”.
6. Click on “05 Cell Resp M2 CO2.cmbl”.
7. Allow probe to calibrate and warm up.
Salt Solution Preparation:
Your group will be assigned a particular salt solution to prepare and collect data from.
Record that salt concentration here _____________ grams/100 mL
1. Using a balance, mass the amount of salt assigned (____ grams) using the scoopula and weigh boat.
2. Measure 100 mL of distilled water using a flask. DO NOT USE TAP WATER.
3. Add the salt to the flask of distilled water. Mix until completely dissolved using the stir rod. Set aside.
4. Obtain 10 dry pea seeds and place them in the CO2 collecting bottle. Attach the gas probe and click
on the green start button. Allow the collection of data to run for a few minutes to get a baseline reading.
Record your baseline concentration ______________ ppm
5. Remove the pea seeds from the bottle and place them on a folded paper towel.
6. Fold the towel in half and place it inside a plastic bag. Label the bag with the concentration of salt
(______g/100 mL) and a group ID mark.
7. Using a 25 mL graduated cylinder, measure and add 20 mL of the prepared salt solution to the bag.
8. Remove excess air and seal the bag to prevent evaporation. Place the bag in a secure location.
Initial Baseline
CO2 Concentration
(ppm)
Day ______ CO2
Concentration (ppm)
Day ______ CO2
Concentration (ppm)
Final CO2
Concentration (ppm)
Class Data Set
Concentration of Salt
Solution (g/mL)
Initial Baseline
CO2
Concentration
(ppm)
Day ______
CO2
Concentration
(ppm)
Day ______
CO2
Concentration
(ppm)
Final CO2
Concentration
(ppm)
Graphs: From your data table you should be able to produce a graph either by hand or online.
Construct a line graph on which you compare the concentration of salt solution vs. the rate of gas
production via respiration. Be sure to include a title and label the axes.
Analysis:
1. Does there seem to be a relationship between the rate of respiration (AN INDICATOR OF
GERMINATION) and the concentration of the salt water? If so, what is that relationship … what is the
conclusion from the data analysis?
2. 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?
3. Explain why increasing levels of salt concentrations affect seed growth and why irrigation seems to
be the main cause of this. (Use your textbook or research)
4. Do you think all seeds would be affected in similar ways as the ones you used? Explain.
5. When soil becomes too salty, describe some methods of remediation.