Using the Graphs to determine the TC50
 Make a bar graph for the seed germination.
 Determine the maximum germination rate for the control.
 The toxic concentration 50 (TC50) for germination is the dose that causes half
as much germination.
 Without a line you will not be able to determine an exact TC50 for
germination so you will give a range.
Effect of Chemical X on Lettuce Seed Germination
0%
0.001%
0.01%
0.1%
1%
10%
0.1% < TC50 GERMINATION ≤ 1%
100%
Effect of Chemical X on Radicle Length Growth of Lettuce Plants
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Make a line graph on the semilog graph paper for the growth of the radicle length. Use
percent concentration for your graph. Draw a best fit line or curve
Determine the maximum growth for the control (no toxin).
The TC50 for the radical growth is the dose that causes ½ the growth.
Interpolate the exact dosage from the graph. Show a dotted line on your graph to show your
work that traces where the 50% growth level intersects the line on the graph and then trace
down to the dosage for this level of growth.
This line with show the TC50 for percent concentration. Calculate the dosage in mg/L from
the toxin. Show your work in the space below the graph.
18
Max growth = 18 mm
16
Growth of Radicle (mm)
14
12
10
8
50% growth
6
4
TC 50 for growth = 4%
2
0
0.001
0.01
0.1
1
10
100
Percent Concentration of Chemical X
Show on your graph how you determine the TC50 for and then use the space below to show
your calculations for TC50 in mg/L
100% concentration Chemical X = 16 g/L or 16,000 mg/L
TC 50 = 0.04 x 16,000 = 640 mg/L (.64 g/L)