At 3:49 PM -0500 2/13/98, mclaugh at augsburg.edu wrote:
>I don't know about others who have had students do projects, but my
>experience with "acid rain" projects is that they don't work well. The
>worst thing about them has been the lack of any apparently meaningful
>results, or the opposite of the expected results. That is, the "acid rain"
>plants grow bigger/faster/better than the control plants. Now, one could
>argue that this is all part of the learning experience in science, and I
>certainly agree in principle. But for a project to be completed in a very
>specified and short time, I prefer to suggest several topic areas where I
>am pretty sure meaningful results are likely to be had, let the individual
>student choose from those areas, and then help him/her further refine the
One project we tested was to try to answer the question about
why seeds don't sprout inside tomatoes. It is warm and
moist in there...seems ideal for seed germination.
The project was initiated by trying to sprout lettuce seeds
in tomato juice and water...both in dim light in petri dishes.
Lettuce seeds fail to sprout in tomato juice...95% germination
This led to testing the tomato juice. We measured pH,
osmolarity, and so on.
Then we tried sprouting lettuce seeds in pH buffers
and various concentrations of salt and sugar. We
also did an Abscisic acid dose response. We found
that the simplest explanation was the osmolarity of
the tomato juice was too high for seed germination.
The pH of tomato juice was just about ideal for
seed germination. We didn't need to invoke the AbA
concentration to explain what we observed.
Seed germination does respond to pH but, in the case
of lettuce seeds, lower pH elicited improved rates
of seed germination. Germination was inhibited at
higher pH values.
Ross Koning | koning at ecsu.ctstateu.edu
Biology Department | http://koning.ecsu.ctstateu.edu/
Eastern CT State University | phone: 860-465-5327
Willimantic, CT 06226 USA | fax: 860-465-4479
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