PROBLEM: You are charged with developing a chloride standard to guide road salt application at MSU with the goal of minimizing salt burn to the vegetation on campus.

APPROACH: A bioassay provides information on the toxicity effects on test organisms. You will evaluate the effects of various chloride concentrations on germination rate and radicle length of a commonly used bioassay organism by the Environmental Protection Agency (EPA), buttercrunch lettuce (Lactuca sativa var. Buttercrunch) to guide road salt application on campus.

B. Experimental setup procedure:

1.Label petri dishes (section and group number, treatment level).

2.Cut to size, and place 2 filter papers in each petri dish.

3.With a disposable pipette, add 4 pipettes full of treatment solution to the appropriate petri dish.

4.Evenly spread 10 seeds in each petri dish.

5.Cover petri dishes with lids and place in designated space (do not stack dishes). Make sure the seeds are spread out within the petri dish.

1.(2pt) In an experiment, what is the function of a control? Identify the control of your bioassay.

2.(2pt) Identify the independent variable of your bioassay.

3.(2pt) Identify the dependent variable(s) of your bioassay.

1. (2pt) Hypothesize how you think increasing NaCl concentration will affect (i) germination rate and (ii) radicle length:

(i) As NaCl concentration increases, germination rate _________________________

(ii) As NaCl concentration increases, radicle length ___________________________