Duckweed Dose/Response Bioassay

Data Form


Name __________________________

Date __________________________


Chemical tested ___________________________

100% concentration _____________________ mg/L

Length of experiment _____________________ days

Constants (such as temperature and light) ______________________________________



Table 3a. Duckweed Bioassay Data





# Duckweed Fronds/Beaker


Avg. # Fronds


Comments about Plant Health













































Make a bar graph showing the average number of fronds in each treatment:



Name __________________________


Some questions to consider: (Please answer using full sentences.)



1. Did the duckweed colonies grow well in the control beakers? Do your control plants appear healthy? If not, what would you recommend trying differently for the next round of experiments?









2. Did duckweed growth respond in a predictable way to concentration? Describe any trends you observed.










3. Do any of your data not fit the trends you observed? If so, can you think of any reasons why these data might lie outside the range you would expect?








4. What TC50 would you estimate based on your duckweed data? TC50 = ___

(If it is impossible to estimate the TC50 from your data, please explain why.)










5. What can you conclude about the toxicity of the substance you tested? Is this what you expected? Was your hypothesis supported by the data?








6. If other students carried out a dose/response experiment using the same chemical, did their data follow the same trends as yours?











7. Based on this experiment, would you say that duckweed would be a useful bioassay organism for water samples from the environment? Why or why not?












8. If you were going to repeat this experiment, what would you do differently? How might you improve the experimental design to reduce the variability of your data or lead to more reliable results?









NSTA. Cornell Scientific Inquiry Series. For use with Assessing Toxic Risk, Protocol 3.