The Effects of NaCl on the Germination of Radish Seeds
A Scientific Method Lab
Background:
Farmers in the Central Valley of California have become increasingly concerned about the build-up of salt in the soil & water.
Farmers know that a small amount of salt in the soil & water will not adversely affect the germination & growth of their crops.
But how much is too much??? Salt build-up is an existing or potential hazard on almost all of the 42 million acres of irrigated
farmland in the US. Much of the world’s unused land is in arid & semiarid regions where irrigation will be necessary.
Excessive salinity is presently costing the US billions of dollars. Salt can kill germinating seedlings by removing the water from
their cells. Several salts and their ions are responsible: NaCl, CaCl2 , KCl, MgCl2, MgSO4, HCO3-, CO3-2, MgCO3, NO3-, NH4+, and
K +.
Materials:
1 rectangular container
4 petri dishes
40 radish seeds (10 per petri dish)
Tweezers
Stirring Stick
Dropper
1 grease pencil
4 pieces of filter paper or paper towel
1 paper plate
100 mL beaker
Salt (1g, 2g and 3g)-measured out for you
Procedure: (Don’t forget to take notes in your lab notebook. Keep a detailed description of every step you take so that
someone else could accurately and precisely reproduce your results). See Lab Report Format for how your final Lab Report
should look.
1. Determine what your group’s hypothesis will be and write it as an “if, then” statement on your lab report.
2. Label each petri dish with the 4 different amounts of salt using the grease pencil: (control (0%), 1%, 2% and 3%)
3. To make salt concentrations of 1%, 2% and 3%:
-Place 100 mL of water in beaker
-To make a concentration of 1%, add 1 gram of salt (for 1%=1g and for 2%=2g and for 3%=3g) and stir (dump water
out and start with 100mL of clean water for each concentration!)
4. Place the filter paper in each of the petri dishes and use the dropper to place 35 drops of each concentration in the
correct beaker.
5. Place 10 seeds in each petri dish and put the lid on.
6. Place all 4 petri dishes on the paper plate and label with each group member’s name and place near the window.
Time
Control
1%
2%
3%
Table 1: Number of Seeds Germinated
24 Hours
48 Hours
Guiding Questions to consider when writing your Lab Report (please do not be limited by these questions!):
1. Is there a salinity level at which no effect on the germination of radish seeds is seen?
2. What level carried the greatest reduction on germination?
3. Are there any levels in which the germination rate did not differ from the control?
4. Identify the independent and dependent variable in this experiment. Are there any constants? If so, what?
5. As a result of this simulation, what do you think will happen to crops in the US as irrigated crop land is exposed to
salt? How will this affect your grocery bill in the future?
6. Should your hypothesis be proved or disproved based on your results?
7. How could this experiment be improved?
The Effects of NaCl on the Germination of Radish Seeds
A Scientific Method Lab
Background:
Farmers in the Central Valley of California have become increasingly concerned about the build-up of salt in the soil & water.
Farmers know that a small amount of salt in the soil & water will not adversely affect the germination & growth of their crops.
But how much is too much??? Salt build-up is an existing or potential hazard on almost all of the 42 million acres of irrigated
farmland in the US. Much of the world’s unused land is in arid & semiarid regions where irrigation will be necessary.
Excessive salinity is presently costing the US billions of dollars. Salt can kill germinating seedlings by removing the water from
their cells. Several salts and their ions are responsible: NaCl, CaCl2 , KCl, MgCl2, MgSO4, HCO3-, CO3-2, MgCO3, NO3-, NH4+, and
K +.
Materials:
1 rectangular container
4 petri dishes
40 radish seeds (10 per petri dish)
Tweezers
Stirring Stick
Dropper
1 grease pencil
4 pieces of filter paper or paper towel
1 paper plate
100 mL beaker
Salt (1g, 2g and 3g)-measured out for you
Procedure: (Don’t forget to take notes in your lab notebook. Keep a detailed description of every step you take so that
someone else could accurately and precisely reproduce your results). See Lab Report Format for how your final Lab Report
should look.
1. Determine what your group’s hypothesis will be and write it as an “if, then” statement on your lab report.
2. Label each petri dish with the 4 different amounts of salt using the grease pencil: (control (0%), 1%, 2% and 3%)
3. To make salt concentrations of 1%, 2% and 3%:
-Place 100 mL of water in beaker
-To make a concentration of 1%, add 1 gram of salt (for 1%=1g and for 2%=2g and for 3%=3g) and stir (dump water
out and start with 100mL of clean water for each concentration!)
4. Place the filter paper in each of the petri dishes and use the dropper to place 35 drops of each concentration in the
correct beaker.
5. Place 10 seeds in each petri dish and put the lid on.
6. Place all 4 petri dishes on the paper plate and label with each group member’s name and place near the window.
Time
Control
1%
2%
3%
Table 1: Number of Seeds Germinated
24 Hours
48 Hours
Guiding Questions to consider when writing your Lab Report (please do not be limited by these questions!):
1. Is there a salinity level at which no effect on the germination of radish seeds is seen?
2. What level carried the greatest reduction on germination?
3. Are there any levels in which the germination rate did not differ from the control?
4. Identify the independent and dependent variable in this experiment. Are there any constants? If so, what?
5. As a result of this simulation, what do you think will happen to crops in the US as irrigated crop land is exposed to
salt? How will this affect your grocery bill in the future?
6. Should your hypothesis be proved or disproved based on your results?
7. How could this experiment be improved?