LD50 Lab
Collaborators:
Sam Freeman, Ethan Lee, Ryan Baldwin, Michael Goss, Griffin Matthews, and Environmental Science 1st Period Class
Abstract:
To test the effects of NaCl on vegetation, ten radish sees were placed in six petri dishes with different concentrations of salt and after five days, the percentage of seeds that germinated and the mean length were measured. Five trials were done to ensure accuracy. It was discovered that a small amount of salt actually increased the percentage of germination but a larger amount drastically decreased it. Furthermore, no definite correlation was found regarding the difference in radicle length from the control, although it may be that a higher salt concentration causes more growth (even though this does not make much sense).
Problem:
According to the Carnegie Institute for Science, "salinity affects crops on about 200 million acres (80 million hectares) of arable land and not just in developing countries, but areas such as California as well." Using radish seeds, what is the extent to which salt negatively affects vegetation, especially along roadsides and in nearby streams where salt builds up in high concentrations.
Hypothesis:
If ten radish seeds are placed in six petri dishes with different concentrations of salt, then it will be found that less seeds germinated in the higher concentrations than did in the lower concentrations and in the control because salt negatively affects vegetation growth. Also, the ones that do germinate in the higher concentrations of salt will not be as long as the ones that germinated in the lower concentrations.
Parts of the Experiment:
The Independent variable is the concentration of salt. The Dependent variable is how many seeds germinated and how large they grew (on average). The control group is the petri dish with no salt in it. The experimental groups are the five petri dishes with different salt concentrations.
Materials (for one trial):
6 petri dishes, 60 radish seeds, napkins, water, salt, graduated cylinders
Methods:
1. Prepare the following concentrations using test tubes and beakers
Collaborators:
Sam Freeman, Ethan Lee, Ryan Baldwin, Michael Goss, Griffin Matthews, and Environmental Science 1st Period Class
Abstract:
To test the effects of NaCl on vegetation, ten radish sees were placed in six petri dishes with different concentrations of salt and after five days, the percentage of seeds that germinated and the mean length were measured. Five trials were done to ensure accuracy. It was discovered that a small amount of salt actually increased the percentage of germination but a larger amount drastically decreased it. Furthermore, no definite correlation was found regarding the difference in radicle length from the control, although it may be that a higher salt concentration causes more growth (even though this does not make much sense).
Problem:
According to the Carnegie Institute for Science, "salinity affects crops on about 200 million acres (80 million hectares) of arable land and not just in developing countries, but areas such as California as well." Using radish seeds, what is the extent to which salt negatively affects vegetation, especially along roadsides and in nearby streams where salt builds up in high concentrations.
Hypothesis:
If ten radish seeds are placed in six petri dishes with different concentrations of salt, then it will be found that less seeds germinated in the higher concentrations than did in the lower concentrations and in the control because salt negatively affects vegetation growth. Also, the ones that do germinate in the higher concentrations of salt will not be as long as the ones that germinated in the lower concentrations.
Parts of the Experiment:
The Independent variable is the concentration of salt. The Dependent variable is how many seeds germinated and how large they grew (on average). The control group is the petri dish with no salt in it. The experimental groups are the five petri dishes with different salt concentrations.
Materials (for one trial):
6 petri dishes, 60 radish seeds, napkins, water, salt, graduated cylinders
Methods:
1. Prepare the following concentrations using test tubes and beakers
2. Label the six petri dishes with their number and their concentration of salt (as seen above)
3. Put two napkins together and tear them so they fit inside the petri dish (do this for each dish)
4. Pour the liquids into their corresponding petri dishes
5. Put ten radish seeds on the moist napkin in the petri dish (do this for all six dishes)
3. Put two napkins together and tear them so they fit inside the petri dish (do this for each dish)
4. Pour the liquids into their corresponding petri dishes
5. Put ten radish seeds on the moist napkin in the petri dish (do this for all six dishes)
6. Close the petri dishes and let them sit for five days
Data:
Data:
Above is a chart of the percent germination for just the original trial (my group).
Above is a chart of the percent germination for all five trials.
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Above is a chart of the difference in radicle length (from the control) for just the original trial (my group).
Above is a chart of the difference in radicle length (from the control) for all five trials.
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Data Analysis:
Low doses of salt result in a high percentage of germination, with 1.5 mg/L causing the most. As the dose increases however, the amount of seeds that germinate decreases. Both the original trial and the average of all the trials put together show this same trend, yet the decrease in percentage of germination as the dose increases is much more rapid in the original one.
The original trial and the average of all the trials turned out very differently regarding the difference in radicle length from the control. In the original trial, the difference decreased until 3 mg/L and then started to increase again. In the average, the difference just steadily increased along with the dose. It would make more sense for the average of all the trials to be more correct as it seems rather odd that the difference would just decrease drastically at 3 mg/L, as it did in the original trial. Despite this, I am still skeptical to believe even the average as it also doesn't make sense that an increase in salt would lead to more plant growth.
Conclusion:
As predicted in the hypothesis, higher concentrations of salt generally resulted in lower percentages of germination. What was not predicted, however, was that a small concentration of salt (1.5 mg/L) actually increases the percentage of germination. As for the difference in radicle length, the data suggests that higher salt concentrations actually increase the size of vegetation, contrary to the hypothesis. There is reason to suspect that this correlation is not valid, as many scientific studies from various sources such as the University of Vermont and the University of Minnesota suggest that salt is harmful to plant growth.
The LD50 is somewhere around 8 or 9 mg/L of salt, depending on whether the original trial or the average of all the trials is used. It would be a good idea to repeat this experiment with salt concentrations closer to this amount to perhaps determine a more exact LD50.
The radicle data is not really supported by the germination data. To explain, the germination data shows that salt is generally bad for vegetation, perhaps excluding in small concentrations. The radicle data on the other hand (or at least the average of all five trials), shows exactly the opposite; it shows that salt increases the size of the radicle. As previously mentioned, it is more likely that the radicle data is incorrect because of the large amount of evidence that shows salt negatively affects vegetation. If the experiment was repeated and done with greater accuracy, the graph for the difference in radicle length may look something like this (assuming the same trend shown in the % germination graphs is present):
Low doses of salt result in a high percentage of germination, with 1.5 mg/L causing the most. As the dose increases however, the amount of seeds that germinate decreases. Both the original trial and the average of all the trials put together show this same trend, yet the decrease in percentage of germination as the dose increases is much more rapid in the original one.
The original trial and the average of all the trials turned out very differently regarding the difference in radicle length from the control. In the original trial, the difference decreased until 3 mg/L and then started to increase again. In the average, the difference just steadily increased along with the dose. It would make more sense for the average of all the trials to be more correct as it seems rather odd that the difference would just decrease drastically at 3 mg/L, as it did in the original trial. Despite this, I am still skeptical to believe even the average as it also doesn't make sense that an increase in salt would lead to more plant growth.
Conclusion:
As predicted in the hypothesis, higher concentrations of salt generally resulted in lower percentages of germination. What was not predicted, however, was that a small concentration of salt (1.5 mg/L) actually increases the percentage of germination. As for the difference in radicle length, the data suggests that higher salt concentrations actually increase the size of vegetation, contrary to the hypothesis. There is reason to suspect that this correlation is not valid, as many scientific studies from various sources such as the University of Vermont and the University of Minnesota suggest that salt is harmful to plant growth.
The LD50 is somewhere around 8 or 9 mg/L of salt, depending on whether the original trial or the average of all the trials is used. It would be a good idea to repeat this experiment with salt concentrations closer to this amount to perhaps determine a more exact LD50.
The radicle data is not really supported by the germination data. To explain, the germination data shows that salt is generally bad for vegetation, perhaps excluding in small concentrations. The radicle data on the other hand (or at least the average of all five trials), shows exactly the opposite; it shows that salt increases the size of the radicle. As previously mentioned, it is more likely that the radicle data is incorrect because of the large amount of evidence that shows salt negatively affects vegetation. If the experiment was repeated and done with greater accuracy, the graph for the difference in radicle length may look something like this (assuming the same trend shown in the % germination graphs is present):
Citations:
"Breakthrough: How Salt Stops Plant Growth." Carnegie Institution for Science |. N.p., n.d. Web. 29 Oct. 2013. <http://carnegiescience.edu/news/breakthrough_how_salt_stops_plant_growth>.
Perry, Leonard. "Salt Damage to Plants." Uvm.edu. University of Vermont Extension, n.d. Web. 31 Oct. 2013. <http://www.uvm.edu/pss/ppp/articles/salt1.htm>.
Beckerman, Janna. "Salt Damage on Plants." Umn.edu. University of Minnesota, n.d. Web. 31 Oct. 2013. <http://www1.umn.edu/news/features/2006/UR_80738_REGION1.html>.
"Breakthrough: How Salt Stops Plant Growth." Carnegie Institution for Science |. N.p., n.d. Web. 29 Oct. 2013. <http://carnegiescience.edu/news/breakthrough_how_salt_stops_plant_growth>.
Perry, Leonard. "Salt Damage to Plants." Uvm.edu. University of Vermont Extension, n.d. Web. 31 Oct. 2013. <http://www.uvm.edu/pss/ppp/articles/salt1.htm>.
Beckerman, Janna. "Salt Damage on Plants." Umn.edu. University of Minnesota, n.d. Web. 31 Oct. 2013. <http://www1.umn.edu/news/features/2006/UR_80738_REGION1.html>.