Serial Dilutions

1. Serial Dilutions

2. Moist the paper towels with set amount of solution Get and label your petri dishes Cut two pieces of paper towel and insert one into bottom of petri dish Add 10 to 15 seeds to eachbag using forceps then put 2nd moistened towel over the seeds

3. To make the NaClSTOCKsolution - Add # grams of sodium chloride for percent to beaker and add water to 100 mL 4%NaClStock Solution 4grams NaCl + 100 ml water

4. Get as many test tubes (minus your control) as you have petri dishes for your experiment

5. Add 9 mL of water to each of you test tubes

6. Add 1 mL of Stock Solution to first test tube.

7. Mix the first Tube

8. Take 1 mL of first tube and add to second tube

9. Mix

10. Repeat for your remaining tubes

11. Using a disposable pipette, add solution from stock solution to a petri dish + paper towel– keep track of how much you add because you will need to add the same volume to moisten the other petri dishes

12. Stock Solution

15. Water

18. 0.4 g/mL Solution

21. 0.04 g/mL Solution

24. Etc.

25. Be sure you have labeled each petri dish • Name, % Salt Solution, Seed • Moisten with a measured volume of water the second paper towel and place of the seeds – Remember to use the same volume for each 2nd towel/petri dish combo • Put in dark area for about a week.

26. Data • Determine the percent dead for each concentration. • Graph with the % dead on the y-axis and concentration on the x-axis. • Determine the LD50 or the concentration where 50% of the seeds did not germinate

27. 100 75 Percentage of population killed by a given dose 50 25 LD 50 0 8 10 6 14 12 2 4 16 Dose (hypothetical units)