Problem
How does concentration of saltwater affect radish seed germination?
Hypothesis
The LD 50 will occur when there is 10 mL of water and 10 mL of salt water solution added.
Parts of the Experiment
Independent Variables: Concentration of salt
Dependent Variables: Germination
Controlled Variables: dishes, time, location
Control Group: Zero percent group
Experimental Group: The five dishes with saltwater
Dependent Variables: Germination
Controlled Variables: dishes, time, location
Control Group: Zero percent group
Experimental Group: The five dishes with saltwater
Materials
-6 petri dishes
-6 seeds
-12 napkins
-Water
-Graduated cylinder
-Concentrated Salt Water solution
-6 seeds
-12 napkins
-Water
-Graduated cylinder
-Concentrated Salt Water solution
Procedure
Collecting Data and Plotting Results
- Remove the lid of the control dish. Count the number of seeds that germinated. Calculate the percentage of seeds that germinated and record in Table 2. Note: if fewer than 80% of the seeds in this control sample germinate, this indicates a problem with the experiment.
- Measure the length of the radical for each of the germinating lettuce seeds to the nearest millimeter (mm). Look carefully at each sprout to make sure you are measuring just the root, not the shoot as well.
- Repeat steps 1-2 for each petri dish.
- For each treatment, calculate the mean radical length for each salt solution. Add the total radical lengths for each salt solution and divide by the total number of seeds that germinated. Do not include data from seeds that did not germinate. Record data in column labeled, “Mean Radicle Length (mm).”
5. Make a line graph from the data collected to show a dose-response curve. The horizontal axis should be for the independent variable, dose (concentration of salt solutions). The vertical axis should be for the dependent variable, response (mean radical length). Remember to give the graph a title.
6. To help you answer “Did the radical length increase or decrease in length as compared to the control?” subtract the mean radical length of each treatment from the mean radical length of the control. Record your answers in the column, “Difference in Radicle Length” on the data table.
7. Make a line graph to show the percentage of seeds that germinated for each salt solution.
7. Make a line graph to show the percentage of seeds that germinated for each salt solution.
Conclusion Questions
1. What appears to be the LD 50 for salt for radish seeds? Support your answer with data.
The LD 50 is 12.5 percent salt water solution because at this amount of solution, half of the seeds did not germinate. This can be seen in the seed germination curve.
2. Is your radicle data supported by your germination data? Support your answer with data.
The radicle data does support the germination data. Germination and radicle length both decrease as concentration of salt solution increases. You can see both the "Dose Response Curve" and the "Seed Germination Curve" show a negative correlation with a higher concentration of salt solution.
The LD 50 is 12.5 percent salt water solution because at this amount of solution, half of the seeds did not germinate. This can be seen in the seed germination curve.
2. Is your radicle data supported by your germination data? Support your answer with data.
The radicle data does support the germination data. Germination and radicle length both decrease as concentration of salt solution increases. You can see both the "Dose Response Curve" and the "Seed Germination Curve" show a negative correlation with a higher concentration of salt solution.
General Analysis & Conclusions
Evaluation of Hypothesis: My hypothesis of the LD 50 being 50 percent was incorrect. The LD 50 was actually at the 12.5 percent concentration. I overestimated the amount of seeds that could germinate in salt water which led to my hypothesis that wasn't validated by the data.
Accuracy of Results: Since the seeds are small and difficult to measure with a ruler, some of the radicle lengths may be inaccurate. Also, if some of the petri dishes had more exposure to light it may have contributed to seed germination that didn't occur in the dishes kept at the bottom of the container. The spread of the water inside the dish may also have led to a miscalculation or error in results.
Application: Chemicals can be harmful substances, but they can also provide a lot of help. That's why it is important to practice toxicology to determine what each chemical does and at what dosage does it become dangerous to humans. Toxicologists will determine the LD 50 of a substance on an animal species in order to protect humans from the substance. If more LD 50 tests were imposed on species more similar to humans then we could receive a better representation of what chemicals are harmful to humans and what dosages they begin to cause harm. The LD 50 of a substance can determine the outcome of a population that is exposed to the substance so we should gather the information to better understand the chemicals we use to better protect ourselves and other organisms.
Citation: "How Toxic Is Toxic?" Www.uft.org. N.p., n.d. Web. 24 Mar. 2013.
URL: http://www.uft.org/chapters/lab-specialists/how-toxic-is-toxic
Accuracy of Results: Since the seeds are small and difficult to measure with a ruler, some of the radicle lengths may be inaccurate. Also, if some of the petri dishes had more exposure to light it may have contributed to seed germination that didn't occur in the dishes kept at the bottom of the container. The spread of the water inside the dish may also have led to a miscalculation or error in results.
Application: Chemicals can be harmful substances, but they can also provide a lot of help. That's why it is important to practice toxicology to determine what each chemical does and at what dosage does it become dangerous to humans. Toxicologists will determine the LD 50 of a substance on an animal species in order to protect humans from the substance. If more LD 50 tests were imposed on species more similar to humans then we could receive a better representation of what chemicals are harmful to humans and what dosages they begin to cause harm. The LD 50 of a substance can determine the outcome of a population that is exposed to the substance so we should gather the information to better understand the chemicals we use to better protect ourselves and other organisms.
Citation: "How Toxic Is Toxic?" Www.uft.org. N.p., n.d. Web. 24 Mar. 2013.
URL: http://www.uft.org/chapters/lab-specialists/how-toxic-is-toxic