Were the values for the controls consistent between the 2 experiments?
If not, were the differences between acidic or basic and control levels
greater that the difference between the 2 controls?
My vague recollection from 20 years ago is that measurements of O2
evolution could be pretty variable. I also recall that we so strongly
illuminated the samples that we put our samples in a water-jacketed
vessel but maybe you can get a response from someone with more recent
experience. Also, there is a school of thought that Chlamy are sensitive
to Na+ and K+ should be used instead.
Teresa Dou (teresad at unixg.ubc.ca) wrote:
: I have performed an experiment on the Chlamydomonas by providing them
: different pH levels of medium. The First one is around pH 5 (use dilute
: sulfuric acid + Chlamy. medium); the second one is around pH 9.5 (use
: diluted sodium hydroxide + Chlamy. medium); the third is the control with
: a pH of about 6.5). Then, I added in 3 mL of the solution to 3 mL of
: Chlamydomonas. They are exposed to an equal amount of light (with
: the exact distance from the light source and w/ same voltage light bulbs)
: for 40 minutes. We measured the pH level and the oxygen level before
: and after the experiment. It is noticed that the oxygen level has
: increased for all of them. However, the basic one produced more O2 than
: the control and the acidic one produced less O2 than the control. A week
: before, I performed the same experiment with the same procedures (except
: this time, I approx the distance between the light and the Chlamy. and
: also the pH of the acidic soln is about 5.45), the results are the exact
: opposite. Is the light source the only explanation for the contradicting
: results? Can you suggest other reasons that may explain for this strange
: results? ARe the Chlamy. capable to tolerate an acidic environment (like
: acid rain) better or a basic one( like the commercial use detergents)? Why?
: Are there any books, articles that deal with this particular topic?
: Thank you very much for your help!
: Teresa
