COLLABORATORS
Collaboration was with the whole class
INTRODUCTION/PROBLEM
The LD-50 of a compound, "the individual dose [of that compound] required to kill fifty percent of a population of [organisms]" (Environmental Protection Agency), is calculated by some fields of science in order to evaluate the risks of certain chemical compounds. Scientists calculate the LD-50 of a compound using a dose-response experiment in which different populations of test organisms are exposed to various doses of that compound.After a snow, the snow and ice, melt eventually making water, which becomes concentrated with the brine that was laid on the roads to help melt the ice. This concentrate is absorbed by plants, and also creates runoff. The LD50 Lad, gave a chance to exemplify this process, by putting concentrates of salt and water in zip lock baggies laid with a napkin along with plant seeds. This experiment tests the effect of salt on plants growth, and plants that grow in the banks of the roads. The outcome of this experiment should allude to what type of harmful affects the salt on the road causes the plant life. This experiment will help determine the LD 50 of radish seeds when submerged in different levels of salt water?
HYPOTHESIS
If we test salt on the germination of seeds with varying concentrations of salt and water then the baggies with less than 50% concentration of salt will have more than 50% of seed germinate; whereas the other ziplock baggies with more than 50% concentration of salt will have less than 50% of seeds germinate.
PARTS OF THE EXPERIMENT
Part 1: Preparing Serial Dilutions of a Salt Solution
1. Set up 6 test tubes in a test tube rack and label the tubes with the following salt
concentrations: 12.0 g/L, 6.0 g/L, 3.0 g/L, 1.5 g/L, 0.75 g/L and Control. See Table 1
Salt Solutions.
2. Add 10 mL of distilled water to test tubes #2- 6.
3. Measure 20 mL of the concentrated solution (12.0 g/L) and pour into test tube #1.
4. Transfer 10 mL of salt solution from test tube #1 to test tube #2.
5. Gently swirl test tube #2 to mix the salt solution.
6. Repeat steps 4 and 5 for test tubes #3-5 measuring 10 mL each time. DO NOT add
any salt solution to test tube #6.
7. Measure 10 mL of distilled water into test tube #6 to serve as the control. The control
will indicate whether or not your seeds are viable (capable of growing or
developing).
8. Unless you will be using the solutions right away, cover them tightly with plastic
wrap to prevent water loss through evaporation.
Part 2: Setting up a Dose-Response Experiment
1. Obtain six petri dishes. Label each dish according to the concentration of salt solution
to be tested. See Table 1. Salt Solution Concentrations.
2. Fold a half of sheet of paper towel or coffee filter into quarters. Cut it out so that it
fits into the bottom of the petri dish.
3. Measure 6 ml of salt solution and pour onto the paper towel in the appropriate petri
dish. In the control dish, add 5 mL of distilled water. The purpose of a control is to
identify how well the seeds will grow without any salt.
4. Add 10 radish seeds to each petri dish. Space the seeds out evenly on the paper
towel so that they do not touch each other or the sides of the dish.
5. Place the dishes in a plastic bag and seal it to retain moisture. Label your group/s
name on the outside of the bag.
6. Incubate the seeds in a dark place at a constant temperature (preferably 24.5oC) for 4-
5 days.
T. Inspect radish seeds during incubation period. Record any observations. If the paper
seems 4ry, add a 1 or 2 more millimeters of the appropriate salt solution or distilled
water (control).
Part 3: Collecting Data and Plotting Results
1. Remove the lid of the control dish. Count the number of seeds that germinated
(sprouted). Calculate the percentage of seeds that germinated and record in Table 2.
Radish Seed Results.
2. To measure the length of the radicle (embryonic root), carefully remove the
germinating radish seed from the paper towel in one piece. The radicle may be
growing into the layers of towel and can break if you pull too hard.
3. Measure the length of the radicle for each of the germinating radish 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. In the picture below, you would
measure just the part between the two arrows, not the shoot and cotyledons to the
Ieft. Record data in Table 2. Radish Seed Results.
4. Repeat steps 1-3 for each petri dish.
5. For each treatment, calculate the mean (arithmetic average) radicle length for each
salt solution. Add the total radicle lengths for each salt solution and divide by the total number of seeds that germinated. Record data in column labeled "Mean Radicle Length (mm)" in Table 2. Radish Seed Results.
DATA
Collaboration was with the whole class
INTRODUCTION/PROBLEM
The LD-50 of a compound, "the individual dose [of that compound] required to kill fifty percent of a population of [organisms]" (Environmental Protection Agency), is calculated by some fields of science in order to evaluate the risks of certain chemical compounds. Scientists calculate the LD-50 of a compound using a dose-response experiment in which different populations of test organisms are exposed to various doses of that compound.After a snow, the snow and ice, melt eventually making water, which becomes concentrated with the brine that was laid on the roads to help melt the ice. This concentrate is absorbed by plants, and also creates runoff. The LD50 Lad, gave a chance to exemplify this process, by putting concentrates of salt and water in zip lock baggies laid with a napkin along with plant seeds. This experiment tests the effect of salt on plants growth, and plants that grow in the banks of the roads. The outcome of this experiment should allude to what type of harmful affects the salt on the road causes the plant life. This experiment will help determine the LD 50 of radish seeds when submerged in different levels of salt water?
HYPOTHESIS
If we test salt on the germination of seeds with varying concentrations of salt and water then the baggies with less than 50% concentration of salt will have more than 50% of seed germinate; whereas the other ziplock baggies with more than 50% concentration of salt will have less than 50% of seeds germinate.
PARTS OF THE EXPERIMENT
- The independent variable is the concentration of salt (mg/L) that is added to the radish seeds.
- The dependent variables are the number of seeds that germinate and the average length of each radicle.
- The controlled variables are the materials, the amount of water each plant receives, and the amount of light each plant is exposed to, and the number of radish seeds per bag.
- The control group consists of the seeds exposed to distilled water.
- The experimental group consists of the seeds exposed to various concentrations of salt.
- 6 test tubes
- test tube rack
- pipette
- distilled water
- concentrated salt solution (12.0 grams of table salt per 1 L of distilled water)
- sparkling radishes
- 6-90 mm petri dish
- 3 pieces of unbleached paper towels
- 6 plastic bags
- metric ruler
Part 1: Preparing Serial Dilutions of a Salt Solution
1. Set up 6 test tubes in a test tube rack and label the tubes with the following salt
concentrations: 12.0 g/L, 6.0 g/L, 3.0 g/L, 1.5 g/L, 0.75 g/L and Control. See Table 1
Salt Solutions.
2. Add 10 mL of distilled water to test tubes #2- 6.
3. Measure 20 mL of the concentrated solution (12.0 g/L) and pour into test tube #1.
4. Transfer 10 mL of salt solution from test tube #1 to test tube #2.
5. Gently swirl test tube #2 to mix the salt solution.
6. Repeat steps 4 and 5 for test tubes #3-5 measuring 10 mL each time. DO NOT add
any salt solution to test tube #6.
7. Measure 10 mL of distilled water into test tube #6 to serve as the control. The control
will indicate whether or not your seeds are viable (capable of growing or
developing).
8. Unless you will be using the solutions right away, cover them tightly with plastic
wrap to prevent water loss through evaporation.
Part 2: Setting up a Dose-Response Experiment
1. Obtain six petri dishes. Label each dish according to the concentration of salt solution
to be tested. See Table 1. Salt Solution Concentrations.
2. Fold a half of sheet of paper towel or coffee filter into quarters. Cut it out so that it
fits into the bottom of the petri dish.
3. Measure 6 ml of salt solution and pour onto the paper towel in the appropriate petri
dish. In the control dish, add 5 mL of distilled water. The purpose of a control is to
identify how well the seeds will grow without any salt.
4. Add 10 radish seeds to each petri dish. Space the seeds out evenly on the paper
towel so that they do not touch each other or the sides of the dish.
5. Place the dishes in a plastic bag and seal it to retain moisture. Label your group/s
name on the outside of the bag.
6. Incubate the seeds in a dark place at a constant temperature (preferably 24.5oC) for 4-
5 days.
T. Inspect radish seeds during incubation period. Record any observations. If the paper
seems 4ry, add a 1 or 2 more millimeters of the appropriate salt solution or distilled
water (control).
Part 3: Collecting Data and Plotting Results
1. Remove the lid of the control dish. Count the number of seeds that germinated
(sprouted). Calculate the percentage of seeds that germinated and record in Table 2.
Radish Seed Results.
2. To measure the length of the radicle (embryonic root), carefully remove the
germinating radish seed from the paper towel in one piece. The radicle may be
growing into the layers of towel and can break if you pull too hard.
3. Measure the length of the radicle for each of the germinating radish 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. In the picture below, you would
measure just the part between the two arrows, not the shoot and cotyledons to the
Ieft. Record data in Table 2. Radish Seed Results.
4. Repeat steps 1-3 for each petri dish.
5. For each treatment, calculate the mean (arithmetic average) radicle length for each
salt solution. Add the total radicle lengths for each salt solution and divide by the total number of seeds that germinated. Record data in column labeled "Mean Radicle Length (mm)" in Table 2. Radish Seed Results.
DATA
DATA ANALYSIS
When looking at the data key trends were discovered: On average, radish seeds exposed to 12 mg/L and 24 mg/L of salt both tended to have short radicle lengths. Also, exposing radish seeds to 3 mg/L of salt led to the germination of 93% of the seeds and radicle lengths 34.7 mm greater than those of the control group, while exposing seeds to 24 mg/L of salt led to the germination of 85% of the seeds and radicle lengths 14.2 mm greater than those of the control group. However, there may have been a possible skew in the data of the experiment: many of the radish seeds exposed to 24mg/L of salt still germinated and had radicles longer than those of the control group. It can be predicted that the LD-50 of salt on radish seeds must be greater than 24 mg/L, and after extrapolating the data onto a dose-response curve, the LD-50 of salt on radish seeds was predicted to be 47.25 mg/L. Also, as seen in pictures 2 (24 mg/L) and 5 (12 mg/L) the bulbs of the radish seeds are darker than the rest of the bulbs in the pictures with lower concentrations of salt. There seems to be a high correlation between high concentrations of salt and the color of the bulbs. Due to the fact that the radishes exposed to 24mg/L of salt still had 85 percent germination and and still had radicals longer than the control group, it is possible that the data was skew
CONCLUSION
According to the data, my hypothesis was incorrect because seeds that were watered with more the 50% of salt still had over 50% germination. The data shows that the average percent of radish seeds that germinated after being watered with each concentration of salt did not reach 50%; the lowest percentage of seeds that germinated, 85%, resulted from watering them with 24 mg/L salt. It can be concluded that the LD-50 of salt on radish seeds must be greater than 24 mg/L, and after deducing the data onto a dose-response curve, the LD-50 of salt on radish seeds was predicted to be 47.25 mg/L.
What can also be concluded is that the higher the salt concentration the darker the bulb of the radish seed.
Also it can the data shows that concentrations less then 3 mg/L of salt are not toxic since 93 percent of those seeds germinated which is the same as the control group. Lastly, higher concentrations of salt do not effect the length of the radicals but the color of the bulbs as seen in pictures 2 and 5.
CITATION
"Lethal Dosage (LD50) Values." EPA. Environmental Protection Agency, n.d. Web. 20 Sept. 2014.
When looking at the data key trends were discovered: On average, radish seeds exposed to 12 mg/L and 24 mg/L of salt both tended to have short radicle lengths. Also, exposing radish seeds to 3 mg/L of salt led to the germination of 93% of the seeds and radicle lengths 34.7 mm greater than those of the control group, while exposing seeds to 24 mg/L of salt led to the germination of 85% of the seeds and radicle lengths 14.2 mm greater than those of the control group. However, there may have been a possible skew in the data of the experiment: many of the radish seeds exposed to 24mg/L of salt still germinated and had radicles longer than those of the control group. It can be predicted that the LD-50 of salt on radish seeds must be greater than 24 mg/L, and after extrapolating the data onto a dose-response curve, the LD-50 of salt on radish seeds was predicted to be 47.25 mg/L. Also, as seen in pictures 2 (24 mg/L) and 5 (12 mg/L) the bulbs of the radish seeds are darker than the rest of the bulbs in the pictures with lower concentrations of salt. There seems to be a high correlation between high concentrations of salt and the color of the bulbs. Due to the fact that the radishes exposed to 24mg/L of salt still had 85 percent germination and and still had radicals longer than the control group, it is possible that the data was skew
CONCLUSION
According to the data, my hypothesis was incorrect because seeds that were watered with more the 50% of salt still had over 50% germination. The data shows that the average percent of radish seeds that germinated after being watered with each concentration of salt did not reach 50%; the lowest percentage of seeds that germinated, 85%, resulted from watering them with 24 mg/L salt. It can be concluded that the LD-50 of salt on radish seeds must be greater than 24 mg/L, and after deducing the data onto a dose-response curve, the LD-50 of salt on radish seeds was predicted to be 47.25 mg/L.
What can also be concluded is that the higher the salt concentration the darker the bulb of the radish seed.
Also it can the data shows that concentrations less then 3 mg/L of salt are not toxic since 93 percent of those seeds germinated which is the same as the control group. Lastly, higher concentrations of salt do not effect the length of the radicals but the color of the bulbs as seen in pictures 2 and 5.
CITATION
"Lethal Dosage (LD50) Values." EPA. Environmental Protection Agency, n.d. Web. 20 Sept. 2014.