Salinization of Soils Paper In this laboratory exercise, you will learn about soil salinization and how plants are affected by elevated salt levels in soil. You will attempt to grow bean plant seeds i

Exercise 1 Salinization of Soils

In this experiment, you will to germinate beans using water with varying salt concentrations. You will then analyze the relationship between germination success and salinity.

Procedure

1. Put on your safety goggles and gloves.

2. Label the lids of the Petri dishes 0.0%, 0.5%, 1.0%, 1.5%, and 2.0% with the permanent marker.

3. Use scissors to cut paper towels into 10 disks of the same diameter as a Petri dish bottom.

4. Place two paper towel disks into the bottom of each Petri dish.

5. Evenly distribute 10 beans on top of the paper towel disks in each Petri dish. See Figure 7.

Figure 7. 

Ten beans evenly distributed on top of paper towel disks inside a Petri dish.

Note: View the video "Using the Digital Scale" before continuing the exercise.

If needed, a descriptive text transcript is available.

Using the Digital Scale

Using the Digital Scale

Volume 90%

This video demonstrates how to use the digital scale.

1. Prepare the 2.0% saline solution:

   1. Place the 100 mL glass beaker on the scale and tare the scale.

   2. Weigh 1.0 g of salt (NaCl) in the 100 mL glass beaker.

   3. Remove the glass beaker containing the salt from the scale.

   4. Add distilled water to the 25 mL graduated cylinder until it reaches the 20.0 mL mark.

   5. Use the long, thin stem pipet to add distilled water to the graduated cylinder until it reaches the 25.0 mL mark.

   6. Pour the salt water solution into the 100 mL beaker.

   7. Use the glass stir rod to mix the solution in the beaker until the salt completely dissolves.

   8. Use the graduated cylinder and pipet to measure 25.0 mL distilled water and pour the distilled water into the beaker containing the salt water solution. 

Note: the 100 mL beaker should now contain 50.0 mL of solution.

1. Use the graduated cylinder to measure 10.0 mL of the 2.0% saline solution from the beaker.

2. Pour the saline solution from the cylinder onto the paper towel disks and beans in the 2.0% Petri dish.

3. Rinse the graduated cylinder and pipet with distilled water.

4. Prepare the 1.5%, 1.0%, 0.5%, and 0% saline solutions according to Table 1:

   1. Use the graduated cylinder and pipet to measure the volume of the 2.0% saline solution listed in Table 1 from the beaker.

   2. Add distilled water as indicated in Table 1 so that the total solution volume in the cylinder measures 10.0 mL.

   3. Pour the saline solution from the cylinder onto the contents of the matching Petri dish.

   4. Rinse the graduated cylinder and pipet with distilled water.

Table 1. 

Solution preparation.

1. 1.  

   2.  

   3.  

   4.  

2. Weigh each of the Petri dishes complete with seeds and solution (but without the lids) on the digital scale.

3. Write the weight of the Petri dish/seed assembly on the Petri dish lid.

4. Cover each dish with its labeled lid and place in a dark area that will not be disturbed. See Figure 8.

Figure 8. 

Final setup for this experiment.

1. After 24 hours remove the lid and determine the mass of the 0.0% dish using the digital scale.

2. While the dish is on the scale, use the pipet to add enough distilled water to return the dish to the mass recorded on its lid.

3. Use a paper towel to wipe any condensation from the underside of the lid before returning the lid to the Petri dish.

4. Repeat steps 14–16 for the remaining four Petri dishes.

5. Repeat steps 14–17 every day for four additional days.

6. Five days after beginning the experiment, determine the germination status of the beans in each Petri dish using the examples shown in Figure 9.

Figure 9. 

Germination classification of bean seeds after five days. Completely germinated seeds have both roots and stems emerged from the seed coat. Incompletely germinated seed have only a small root emerged from the seed coat. Non-germinated seeds have an intact seed coat.

1. Record the total number of seeds in each dish that display complete germination, incomplete germination, or no germination in Data Table 1.  

2. Create a graph illustrating the relationship between salt concentration and the number of seeds germinating.

3. Write your name and date on a sheet of paper.

4. Take a photo of the five Petri dishes on the sheet of paper so that your name and date are displayed.

5. Upload the image into Photo 1.

6. Upload an image of the graph into Graph 1.

Cleanup:

• Wash the graduated cylinder and beaker with soap and water and dry thoroughly.

• Dispose of the Petri dishes and beans in a trash bin.

• Return equipment to the kit for future use.

Exercise 1 - Questions

Question 1

Explain why salinization is a concern for agriculture around the globe.

Question 2

What was the purpose of using distilled water instead of tap water in this experiment?

Question 3

Why were the Petri dishes containing the beans weighed at 24-hour intervals?

Question 4

What was the minimum salt concentration that affected bean germination in your results? Reference Data Table 1 in your answer.

Question 5

Based on your results, would you categorize the bean species used in this experiment as a halophyte or glycophyte. Include the definition of each term in your answers.