Do Lettuce Seeds Provide a Good Bioassay for Salt Toxicity?

1. Do Lettuce Seeds Provide a Good Bioassay for Salt Toxicity? Katie Schneider Grade 9 Academy of Notre Dame de Namur

2. Problem • Do lettuce seeds provide a good bioassay for salt toxicity and at what point would you encounter salt toxicity?

3. Research • Bioassay-a procedure for determining the concentration, purity, and/or biological activity of a substance by measuring its effect on an organism, tissue, cell, enzyme or receptor preparation compared to a standard preparation. • If salt is present in the soil, it absorbs water, therefore depriving the plants of the water needed for sufficient growth • When salt dissolves in water, sodium and chloride separate. This creates high ion charges, increasing its toxicity when it builds up in plants

4. Hypothesis • If there is a large percentage of NaCl in the solution, it will negatively affect the germination of the seeds, and if there is a very small amount of NaCl in the solution, it will aid the germination of the seeds.

5. Materials • 10 mL bleach • 1130 mL distilled water • 18 paper filters • 90 lettuce seeds • 18 petri dishes • 1 1000 mL beaker • 5 100 mL beakers • 11.69 grams of NaCl

6. Procedure • 11.69 grams of NaCl was mixed with distilled water to make a liter of a 0.2 M NaCl solution • 50 mL of the NaCl solution was mixed with 50 mL of distilled water to make a 0.1 M NaCl solution • 37.5 mL of the NaCl solution was mixed with 62.5 mL of distilled water to make a 0.075 M NaCl solution • 25 mL of the NaCl solution was mixed with 75 mL of distilled water to make a 0.05 M NaCl solution • 12.5 mL of the NaCl solution was mixed with 87.5 mL of distilled water to make a 0.025 M NaCl solution • 100 mL of distilled water was used for the control • 10 mL of bleach was combined with 30 mL of distilled water

7. Procedure • The lettuce seeds were placed in the bleach solution for 20 minutes • A paper filter was placed in each petri dish • Each dish was labeled with a number and percentage of NaCl or if it is a control • 2 mL of the appropriate solution was added to each dish • 5 lettuce seeds were evenly spaced in each dish so that they did not touch one another or the sides of the dish • The dishes were placed in a dark place at a constant temperature for 1 day • Observations were then made and recorded

8. Procedure • Each of the 6 solutions was tested 3 times • Independent variable-the percentage of NaCl in each of the solutions • Dependent variable-the number of seeds germinated in each petri dish • Control-the seeds in distilled water • Constants-size of the petri dishes, size of the paper filters, amount of light the seeds got, the amount of liquid the seeds were tested in, and the amount of time before observation

9. Data

10. Data

11. Conclusion • Hypothesis-If there is a large percentage of NaCl in the solution, it will negatively affect the germination of the seeds, and if there is a very small amount of NaCl in the solution, it will aid the germination of the seeds. • The hypothesis was partly supported • Yes, lettuce seeds provided a good bioassay-they would be a good thing to use when testing other compounds • To improve experiment: • Use different types of seeds • Other compounds like phosphorous and nitrogen

12. Thanks for listening! • “bioassay.” ChemiCool. N.p., n.d. Web. 11 Oct. 2010. <http://www.chemicool.com//‌bioassay.html>. • “Bioassay Test for Toxicity.” Home Science Tools. N.p., 2010. Web. 11 Oct. 2010. <http://www.hometrainingtools.com/‌bioassay-test-toxicity-project//‌/>. • “Conducting Reference Toxicity Tests with Lettuce Seeds.” Environmental Inquiry. N.p., 2009. Web. 11 Oct. 2010. <http://ei.cornell.edu/‌toxicology///.html>. • “Everything you Ever Wanted to Know about Salt.” Alternative Medicine Angel. N.p., 1 Jan. 2000. Web. 11 Oct. 2010. <http://altmedangel.com/.htm>. • Perry, Dr. Leonard. "Salt Damage to Plants." University of Vermont Extension. N.p., n.d. Web. 13 Feb. 2011. <http://www.uvm.edu/pss/ppp/articles/ salt1.htm>. • “The Lettuce Seed Bioassay.” Aquatox 2000. N.p., n.d. Web. 11 Oct. 2010. <http://archive.idrc.ca////‌d_lettuce1.html>.