Bioassays Using Duckweed |
Duckweed Bioassays: Compounds and Concentrations
You can use bioassays to measure the sensitivity of duckweed to a wide variety
of compounds, or different concentrations of the same compound. Below is information
on how to create a range of concentrations (serial dilutions) of a compound
you would like to test, as well as examples of different compounds you may
be interested in using.
Creating serial dilutions
The
first step in carrying out a dose/response experiment is to create a wide range
of concentrations of your test solution. Initially, you probably will have
no idea what concentrations will kill your test organisms and what concentrations
will cause them no harm. Therefore, it is a good idea to start by testing a
very wide range of concentrations. You can do this by creating a serial dilution
- a series of solutions, each of which is ten times more dilute than the one
from which it is made.
The highest concentration in your serial dilution will be labeled, "100% Concentration". This can be whatever concentration you choose - just remember to write down what chemical you are using and what concentration (in mg/L) you have selected to be the 100% concentration. The table below has suggestions for possible 100% concentrations.
Compound
|
Suggested 100% Concentration for Lettuce Seeds*
|
Relevance to Environmental Issues
|
Safety Considerations
|
|
NaCl | 12 g/L | Used for highway deicing | None | |
MgCl2 CaCl2 KCl |
12 g/L | Used as "environmentally friendly" alternatives to road salt | Slightly toxic by ingestion | |
CuSO4 | 500 mg/L | Used for weed control in ponds and lakes | Skin and respiratory irritant; moderately toxic by ingestion and inhalation | |
* For bioassays with duckweed or other bioassay organisms, different maximum concentrations may be more appropriate. Each species has its own range of sensitivity. |
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University and Penn State University |