Collaborators:
Katie Lowe, Serena Spencer, Nicole Walker
Introduction:
The LD-50 is "a standard measurement of acute toxicity that is stated in milligrams of pesticides per kilogram of body weight". A LD-50 represents the individual dose required to 50 percent of a population of test animals. The LD-50 standard is used today by many branches of science. For instance, scientists utilize the LD-50 to evaluate hazards of a chemical compound. In doing so they create a dose-response experiment, thus creating a dose-response curve. A dose-response curve is a curve plotting the relationship between the dose of a drug administered and its pharmacological effect. However in order to complete the dose response curve, one must have data. Data can be acquired through a series of dilution of a substance in solution, which will then lower the dosage and add more water to the substance, also known as a serial dilution. In the lab presented below for each water solution a different concentration is added to the seeds. This experiment was made evident due to recent news of salt being applied to highways will then results to impeding plant growth. Originally salt is added to highways to provide tractions for cars, and to melt snow. By orchestrating this LD-50 lab on radish seeds the concentration of salt that is lethal to plant growth will be determined, which may help reduce risks of adding salt to roads, by reevaluating the dose added to roads.
Problem:
What is the LD50 of salt for radish seeds?
How does salt affect the initial growth of radish plants?
How does salt affect the initial growth of radish plants?
Hypothesis:
If the radish seed is placed in a number of containers with salt concentrations, then the seeds placed into a higher concentration will decline the growth. Seeds will not be as germinated with radicles because runoff excess of salt impedes plant growth. The LD-50 set will be 12 mg.
Parts of Experiment:
- The independent variable is the concentration of salt added to the radish seeds.
- The dependent variables are the percent of seeds germinated and the length of radicles.
- The control variables are the number of seeds put into the containers, the amount of water in each seeds receive. and the amount of light each seeds is exposed to
Materials:
- Paper Towels
- Distilled Water
- 24 mg/L Salt Concentrations
- 60 Cherry Belle - Radish seeds
- 6 Petri Dishes
- 10 ml Graduated Cylinder
- 1 Metric Ruler
- 6 Water Containers
- Labeling tape
Methods:
- Using 20 ml of the original concentration of salt, perform a serial dilution to create five different salt concentrations, plus a sixth with plain water.
- Count out 60 seeds, 10 for each water sample.
- Put 10 seeds into a folded paper towel, space the seeds out evenly on the paper towel so that they do not touch each other.
- Wet the paper towel/seeds and seal in a petri dish, be sure to label the petri dish with the salt concentration for that sample.
- After 4-5 days examine the seeds, counting the number of each that germinated.
- For the germinated seeds, measure the length of the radicle.
Data: |
Analysis:The control group had 100 percent germination, averaging 38.1 for radicle length. While the second dosage of 1.5 had 90 percent germination, averaging 12.5 radicle length. Concentrations ranging from 3 mg/L to 24 mg/L had zero percent germination. The difference in radicle lengths is 25.6. In conclusion, this is due to the higher salt concentration placed and applied to group 2 of the control groups.
Furthermore, the seeds grew faster and healthy with distilled water, producing long radicles with green buds on the ends. Contrastingly, to group two, the radicles were shorter than group one by a large deviation and had brown/yellow buds. This can conclude that plants may be harmed from salt concentrations, but may still grow even when unhealthy. The higher the dose the more lethal it is to the plant. |
Pictures:
Conclusion:
As a result of this experiment, it was concluded that the LD-50 dose for radish seeds is well before the set limit. In the stated hypothesis, the LD-50 is set at 12 mg/L, rejecting my hypothesis. However, the average of radish seeds that germinated after being exposed to each concentration of salt did not reach the 50 mark. Instead, the radish seeds stopped germinated after a concentrated dose of 1.5 mg. Therefore, the LD-50 of salt concentration applied to radish seeds is actually 3 mg/L where no germination took place. The concentration of salt that germinated with the highest percentage of seeds and longest radicles is 1.5. The percentage of seeds that had germination was also the same as the control group, thus concluded concentrations of salt less than 3 mg/L will still produce a germinated radish seed. Lastly, radish seeds originally produce healthy looking green buds. However as the concentration grew the plants vitality dropped producing an unhealthy looking yellow buds due to salt.
In addition to the question, "Did the radicle length increase or decrease in length as compared to the control?". The radicle length of the first concentration decreased compared to the control group. In the control group the radicle length averaged 38.1 mm. While the first dose of concentration salt solution averaged about 12 .5 mm in length. There was a difference in radicles of 25.6 mm.
Furthermore, concentrations of salt used to defrost the roads when snow falls is a higher amount compared to the doses applied to the radish seeds. It can be anticipated that runoff will be asserted to plants nearby, causing them severe harm, hindering them from their growth. It is said, "Deicing salt is usually refined rock salt consisting of about 98.5 percent sodium chloride, 1.2 percent calcium sulfate, 0.1 percent magnesium chloride, and 0.2 percent rock". As a result from studies conducted, certain measures have been construed to aid this issue. Such as, "If vegetation is located in areas where salt spray occurs, erect barriers or screens to protect plants during the winter months".
In addition to the question, "Did the radicle length increase or decrease in length as compared to the control?". The radicle length of the first concentration decreased compared to the control group. In the control group the radicle length averaged 38.1 mm. While the first dose of concentration salt solution averaged about 12 .5 mm in length. There was a difference in radicles of 25.6 mm.
Furthermore, concentrations of salt used to defrost the roads when snow falls is a higher amount compared to the doses applied to the radish seeds. It can be anticipated that runoff will be asserted to plants nearby, causing them severe harm, hindering them from their growth. It is said, "Deicing salt is usually refined rock salt consisting of about 98.5 percent sodium chloride, 1.2 percent calcium sulfate, 0.1 percent magnesium chloride, and 0.2 percent rock". As a result from studies conducted, certain measures have been construed to aid this issue. Such as, "If vegetation is located in areas where salt spray occurs, erect barriers or screens to protect plants during the winter months".
Citations:
Impact of Road Salt on Adjacent Vegetation." Plant Pest Advisory. N.p., n.d. Web. 1 Feb. 2015.
"Lethal Dosage (LD50) Values." EPA. Environmental Protection Agency, 27 June 2012. Web. 03 Feb. 2015
<http://www.epa.gov/oecaagct/ag101/pestlethal.html>.
Perry, Leonard. "Salt Damage to Plants." University of Vermont. N.p., n.d. Web. 13 Sept. 2014. <http://www.uvm.edu/pss/ppp/articles/salt1.htm>.
"Lethal Dosage (LD50) Values." EPA. Environmental Protection Agency, 27 June 2012. Web. 03 Feb. 2015
<http://www.epa.gov/oecaagct/ag101/pestlethal.html>.
Perry, Leonard. "Salt Damage to Plants." University of Vermont. N.p., n.d. Web. 13 Sept. 2014. <http://www.uvm.edu/pss/ppp/articles/salt1.htm>.