Jon Monroe monroejd at
Wed Sep 9 10:27:26 EST 1998


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? :-)


>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

  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

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