David,
Your symbiosis lab sounds really nice. I wonder if you could try using a
legume with small seeds which would cause them to run out of stored N
faster, and perhaps take up even less greenhouse space? (Too bad
Arabidopsis isn't a legume, eh? :-)
Jon
>In our Plant Biology 102 Introductory Plant Biology course (second quarter
>of a two-quarter course for non majors) the students do an experiment with
>soybean/Rhizobium symbiosis. We grow inoculated and uninoculated soybeans
>in high nitrogen/low nitrogen soil. (The experiment uses minimal
>greenhouse space because each team of two students sets up four 4-inch pots
>with two soybeans each: H+, H-, L+, L-.) At the end of approximately 7
>weeks we terminate the experiment and assay for shoot weight, number of
>nodules, and nodule weight (size). As you know, soybean will not form the
>association with Rhizobium in high nitrogen soils. The experimental
>results consistently confirm this. However, we do not see major
>differences in the shoots (qualitative or quantitative) because in this
>early developmental phase (first 7 weeks) the plants are producing
>relatively little protein (i.e., require less nitrogen) compared with the
>amount they will be producing during seed maturation. Unfortunately we do
>not have enough time in the quarter to run the experiment to that stage of
>development. Nevertheless, the experiment is easy for our non-majors to
>understand and it generates a lot of discussion about symbiosis, feedback
>mechanisms, etc.... not to mention a discussion of the need for ag research
>(a hidden agenda!) at our Ohio Agricultural Research and Development Center
>operated by OSU at Wooster, OH. By the way, the students also cut open a
>nodule to see the pink interior. This is leghemoglobin which binds O2 to
>create an anaerobic environment for the Rhizobium. This ties into our
>discussion of aerobic and anaerobic cellular respiration.
>>If you would like a copy of the exercise, I could fax or mail it to you.
>>>>>Dr. David W. Kramer
>Department of Evolution, Ecology,
> and Organismal Biology
>Ohio State University at Mansfield
>1680 University Drive
>Mansfield, OH 44906-1547
>(419) 755-4344 FAX: (419) 755-4367
>e-mail: kramer.8 at osu.edu
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Jonathan Monroe
Associate Professor
Department of Biology
James Madison University
Harrisonburg, VA 22807
voice: 540-568-6649 (office)
540-568-6045 (lab)
fax: 540-568-3333
e-mail: monroejd at jmu.edu
csm.jmu.edu/biology/monroejd/jmonroe.html
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