LD 50 Lab
Collaborators- Sam Freeman, Griffin Matthews, Ryan Baldwin, Michael Goss, Environmental Science 1st Period Class.
Abstract- An experiment was conducted to test the effect of NaCl on plants. The experiment sought the lethal dose needed to kill 50% of the plant population (LD 50). Six petri dishes, each with ten seeds, were set with different concentrations of NaCl for five days. After the five days, the mean lengths of the radicles were calculated. The eight groups in the lab then averaged the means to find the average LD 50 for the radish seeds.
Problem- According to the Carnegie Institute for Science, "salinity affects crops on about 200 million acres (80 million hectares) of arable land." Using the radish seeds, find the lethal dose needed to kill 50% of the vegetation (LD 50).
Hypothesis- The higher the salt concentration, the less seeds will germinate because the salt will impair their growth.
Parts of experiment- Independent variable- salt concentrations in the water
Dependent variable- amount of seeds germinated and length of radicles
Control- petri dish with no salt in the water.
Materials- 6 petri dishes
60 radish seeds
napkins
water
salt
graduated cylinders
Methods-
1. Prepare the following concentrations using test tubes and beakers:
Abstract- An experiment was conducted to test the effect of NaCl on plants. The experiment sought the lethal dose needed to kill 50% of the plant population (LD 50). Six petri dishes, each with ten seeds, were set with different concentrations of NaCl for five days. After the five days, the mean lengths of the radicles were calculated. The eight groups in the lab then averaged the means to find the average LD 50 for the radish seeds.
Problem- According to the Carnegie Institute for Science, "salinity affects crops on about 200 million acres (80 million hectares) of arable land." Using the radish seeds, find the lethal dose needed to kill 50% of the vegetation (LD 50).
Hypothesis- The higher the salt concentration, the less seeds will germinate because the salt will impair their growth.
Parts of experiment- Independent variable- salt concentrations in the water
Dependent variable- amount of seeds germinated and length of radicles
Control- petri dish with no salt in the water.
Materials- 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.
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)
Data-
Data Analysis- Lower doses of NaCl seem to cause the highest % germination with 1.5 mg/L causing the highest % germination. As the dose increases, the % germination lowers. When looking at the average % germination for the five groups, none of the NaCl dosages reached the LD 50. However, in the individual group, the LD 50 for the group was about 7 mg/L of NaCl. Another trend worth noting is the radicle lengths. The radicle lengths seemed to become longer as the concentration of NaCl increased. This may be because there was less competition for water so the remaining radish radicles could grow to be longer.
Conclusion- The concentration of NaCl in water does affect the growth of radishes. The germination is affected and it becomes harder for the radishes to sprout as NaCl is harmful to plant life. However, is they do grow, the salt does not affect them as much and therefore are able to grow, now able to use more water with less competition in their environment.
There were some random spikes and drops in the graphs and they could have been caused for several reasons. The seeds could have been larger and not as affected by the amount of salt in the water. The placement of the seeds also could have kept it from the large amounts of salt. It could also have been human error in measuring the lengths or amount of salt in the water.
Questions-
1. What appears to be the LD 50 for salt for radish seeds? Support your answer with data. The LD 50 for NaCl for the radish seeds appears to be 7 mg/L in the individual group lab, but when averaged with the rest of the groups, the LD 50 appears to be around 14 mg/L. I suppose it depends on the seed's placement, possible abnormal resistance, and/or size. This can be supported as the % germination in each dish were rather sporadic and different variables could have affected it.
2. Is your radicle data supported by your germination data? Support your answer with data.
Yes, because with less radicles in the environment taking up water, more water would be available for the remaining radicles, allowing them to grow longer.
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>.
Conclusion- The concentration of NaCl in water does affect the growth of radishes. The germination is affected and it becomes harder for the radishes to sprout as NaCl is harmful to plant life. However, is they do grow, the salt does not affect them as much and therefore are able to grow, now able to use more water with less competition in their environment.
There were some random spikes and drops in the graphs and they could have been caused for several reasons. The seeds could have been larger and not as affected by the amount of salt in the water. The placement of the seeds also could have kept it from the large amounts of salt. It could also have been human error in measuring the lengths or amount of salt in the water.
Questions-
1. What appears to be the LD 50 for salt for radish seeds? Support your answer with data. The LD 50 for NaCl for the radish seeds appears to be 7 mg/L in the individual group lab, but when averaged with the rest of the groups, the LD 50 appears to be around 14 mg/L. I suppose it depends on the seed's placement, possible abnormal resistance, and/or size. This can be supported as the % germination in each dish were rather sporadic and different variables could have affected it.
2. Is your radicle data supported by your germination data? Support your answer with data.
Yes, because with less radicles in the environment taking up water, more water would be available for the remaining radicles, allowing them to grow longer.
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>.