LD-50 Lab
Collaborators-
Griffin Matthews, Ethan Lee, Michael Goss, Sam Freeman, Ryan Baldwin. Data compilation from Mr. Gunsher's 1st period AP Environmental Science class in its entirety.
Griffin Matthews, Ethan Lee, Michael Goss, Sam Freeman, Ryan Baldwin. Data compilation from Mr. Gunsher's 1st period AP Environmental Science class in its entirety.
Abstract-
An experiment was conducted to test what concentration of salt is lethal to 50% of the radish seeds subjected to salt (LD-50). Six petri dishes were set up with varying concentrations of salt within them: 0% (control), 6.25%,12.5%, 25%, 50%, and 100% concentration. Each petri dish contained 10 seeds and was left with the water and salt mix for 5 days (Monday-Friday). 5 days later, the group removed the seeds and counted the seeds that had germinated for each concentration as well and measured the radicles on each seed that had germinated and averaged the numbers. The results followed the class trends fairly well but the group usually had less seeds germinate. This is due to a probable mistake in the experiment set up in regards to concentration. The class data supports the notion that 12.5% salt concentration is the best concentration of salt for plant seeds to thrive in.
An experiment was conducted to test what concentration of salt is lethal to 50% of the radish seeds subjected to salt (LD-50). Six petri dishes were set up with varying concentrations of salt within them: 0% (control), 6.25%,12.5%, 25%, 50%, and 100% concentration. Each petri dish contained 10 seeds and was left with the water and salt mix for 5 days (Monday-Friday). 5 days later, the group removed the seeds and counted the seeds that had germinated for each concentration as well and measured the radicles on each seed that had germinated and averaged the numbers. The results followed the class trends fairly well but the group usually had less seeds germinate. This is due to a probable mistake in the experiment set up in regards to concentration. The class data supports the notion that 12.5% salt concentration is the best concentration of salt for plant seeds to thrive in.
Problem-
What is the LD-50 (lethal dose that kills 50% of the seeds) of salt on the radish seeds?
What is the LD-50 (lethal dose that kills 50% of the seeds) of salt on the radish seeds?
Hypothesis-
If we test radish seed growth (% germination and radicle length) in different concentrations of salt, then, the more concentrated the salt, the more limited the radish seed germination and radicle length will be.
If we test radish seed growth (% germination and radicle length) in different concentrations of salt, then, the more concentrated the salt, the more limited the radish seed germination and radicle length will be.
Parts of Experiment-
Control Group- The petri dish with pure water and 0% salt concentration
Experimental Group- The 5 petri dishes with varying degrees of salt concentration
Independent Variable- Concentration of salt solution
Dependent Variable- Mean radicle length and % germinated
Control Group- The petri dish with pure water and 0% salt concentration
Experimental Group- The 5 petri dishes with varying degrees of salt concentration
Independent Variable- Concentration of salt solution
Dependent Variable- Mean radicle length and % germinated
Materials-
6 Petri Dishes
60 Seeds
12 Paper Towels (cut to fit the petri dishes)
6 Varying Concentrations of Salt Water
Water
Graduated Cylinder
Test Tubes
Test Tube Rack
6 Petri Dishes
60 Seeds
12 Paper Towels (cut to fit the petri dishes)
6 Varying Concentrations of Salt Water
Water
Graduated Cylinder
Test Tubes
Test Tube Rack
Methods-
1. Fill six petri dishes each with the necessary amount of salt solution and concentration following this chart:
1. Fill six petri dishes each with the necessary amount of salt solution and concentration following this chart:
2. Label your petri dishes so you know which is which concentration in 5 days.
3. Place moist (moist with the proper salt solution for the corresponding dish) paper towel in all 6 dishes.
4. Place ten seeds in each petri dish and cover again with more paper towel dampened with salt solution.
5. Close and stack the petri dishes face up and store in an untouched location for 5 days.
6. After 5 days, measure the radicle lengths of all germinated seeds in the petri dish and take note of how many seeds germinated.
7. Repeat step 6 for all petri dishes.
3. Place moist (moist with the proper salt solution for the corresponding dish) paper towel in all 6 dishes.
4. Place ten seeds in each petri dish and cover again with more paper towel dampened with salt solution.
5. Close and stack the petri dishes face up and store in an untouched location for 5 days.
6. After 5 days, measure the radicle lengths of all germinated seeds in the petri dish and take note of how many seeds germinated.
7. Repeat step 6 for all petri dishes.
Data-
Group Data
Group % Germinated
Group Radicle Difference from Control
Class Data Averages
Taken from the 6 groups that provided legible data
* Taken from 5 out of 6 groups
Taken from the 6 groups that provided legible data
* Taken from 5 out of 6 groups
Class % Germinated
Class Radicle Difference from Control
Data Analysis-
The group's data has some much more extreme rises and falls in the data chart than the smoother trends of the class data, but this is to be expected. The group's data for the 100% concentration was the lowest in the class at only 10%. It is odd that some other groups had germination rates up to 90% for the 100% concentration of salt. The seeds seemed to thrive most in the 12.5% concentration of salt with an almost 92% germination rate from the class data average. The radicle graph had a seemingly random 50mm radicle length at 12.5% concentration and it is unknown why that could have occurred. Possibly and probably just an irregularity in experiment since it would be a statistical anomaly for there to be a 50mm radical where the next closest radicle length in that concentration was 5mm.
The group's data has some much more extreme rises and falls in the data chart than the smoother trends of the class data, but this is to be expected. The group's data for the 100% concentration was the lowest in the class at only 10%. It is odd that some other groups had germination rates up to 90% for the 100% concentration of salt. The seeds seemed to thrive most in the 12.5% concentration of salt with an almost 92% germination rate from the class data average. The radicle graph had a seemingly random 50mm radicle length at 12.5% concentration and it is unknown why that could have occurred. Possibly and probably just an irregularity in experiment since it would be a statistical anomaly for there to be a 50mm radical where the next closest radicle length in that concentration was 5mm.
Conclusion-
The experiment went fairly well and the group only experienced a few significant inconsistencies and the group's data flowed fairly nicely with the class's data averages. The group generally had the lowest numbers in terms of % germinated that had to be averaged into the class data. This could have been linked to a mistake in salt concentration (too much or too little salt) when setting up the experiment. Also, the group was told how excess water can drown the seeds. When the group opened up the petri dishes, there was quite an excess of water, so this might have been a mistake. (I draw this conclusion since the lab instructions read, "If fewer than 80% germinate in the control then you have a problem with your experiment"). Perhaps a second trial would give the results a bit more credibility.
A reason that salt helped the germination and radicle length in lower concentrations could be caused by the salt acting like a fertilizer. This article (link) explains the different components in fertilizer and some of the main parts are forms of salt. The fertilizer usually doesn't use regular NaCl table salt but use more complicated forms like Sulfur based salts.
The LD-50 is the lethal dose to 50% of those subjected to salt. The LD-50 appears to be about 125% concentration when using class average data. This answer is extrapolated from the data since the class data did not reach 50% lethal dose. In the class data chart (above), the % germinated takes a steep dive when the salt concentration was 100%, so 125% would probably be a reasonably close estimate. The radicle data did support the germination data. When there were few seeds germinating, the radicles that did actually grow were fairly short. The salt concentration was pretty devastating to the radicle growth and germination processes after around the 25% concentration.
The experiment went fairly well and the group only experienced a few significant inconsistencies and the group's data flowed fairly nicely with the class's data averages. The group generally had the lowest numbers in terms of % germinated that had to be averaged into the class data. This could have been linked to a mistake in salt concentration (too much or too little salt) when setting up the experiment. Also, the group was told how excess water can drown the seeds. When the group opened up the petri dishes, there was quite an excess of water, so this might have been a mistake. (I draw this conclusion since the lab instructions read, "If fewer than 80% germinate in the control then you have a problem with your experiment"). Perhaps a second trial would give the results a bit more credibility.
A reason that salt helped the germination and radicle length in lower concentrations could be caused by the salt acting like a fertilizer. This article (link) explains the different components in fertilizer and some of the main parts are forms of salt. The fertilizer usually doesn't use regular NaCl table salt but use more complicated forms like Sulfur based salts.
The LD-50 is the lethal dose to 50% of those subjected to salt. The LD-50 appears to be about 125% concentration when using class average data. This answer is extrapolated from the data since the class data did not reach 50% lethal dose. In the class data chart (above), the % germinated takes a steep dive when the salt concentration was 100%, so 125% would probably be a reasonably close estimate. The radicle data did support the germination data. When there were few seeds germinating, the radicles that did actually grow were fairly short. The salt concentration was pretty devastating to the radicle growth and germination processes after around the 25% concentration.
Citation-
Argo, Bill, and Paul Fisher. "Understanding Plant Nutrition: Fertilizers And Macronutrients | Greenhouse Grower." Greenhouse Grower. Www.greenhousegrower.com, 24 July 2008. Web. 31 Oct. 2013. (Referenced in the conclusion)
Argo, Bill, and Paul Fisher. "Understanding Plant Nutrition: Fertilizers And Macronutrients | Greenhouse Grower." Greenhouse Grower. Www.greenhousegrower.com, 24 July 2008. Web. 31 Oct. 2013. (Referenced in the conclusion)