Serial Dilutions

Get 2 x 3 inch jewelry bags jewelry supply store. See product # on second templates/product_list_dro pdown_pix.aspx?GroupGui d= templates/product_list_dro pdown_pix.aspx?GroupGui d=5523 Cut piece of paper towel and insert into bag Staple across the bag such that there is space for roots to grow Add 10 to 15 seeds to each bag

0.1 g/mL NaCl Stock Solution NaCl STOCK solution Make a 0.1-g/mL NaCl STOCK solution - Add 1 g of sodium chloride to beaker and add water to 10 mL

Get as many test tubes (minus two controls) as you have plastic jewelry bags for your experiment

Add 5 mL of water to each of you test tubes

Add 5 mL of Stock Solution to first test tube.

Mix the first Tube

Take 5 mL of first tube and add to second tube

Mix

Repeat and remove 5 ml from last tube and discard

Using a 5mL disposable pipette, add 3 mL from stock solution to a bag. This is one control bag

Using a 5mL disposable pipette, add 3 mL Water to a bag. This is one control bag.

Using a 5mL disposable pipette, add 3 mL from your dilutions to each remaining bag. These are your variables.

Stock Solution

Water

0.1 g/mL Solution

0.05 g/mL Solution

Etc.

Put all the bags upright in the beaker that had the stock solution. Put in dark area for one about one week 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

Percentage of population killed by a given dose Dose (hypothetical units) LD 50