Dr. Andrew Samuelsen andrews at
Wed Aug 16 09:59:06 EST 2000

Dear Group,
     I'm teaching a Botany course at Albright College in Reading
Pennsylvania.  I am attempting to do a floating leaf disc assay for
photosynthesis based on a paper in the American Biology Teacher 47:
96-99, 1985.  Basically one vacuum infiltrates the discs in a buffer to
make them sink, shine a light on them and then the oxygen they produce
causes them to float (inversely proportional to the photosynthetic
rate).  It looks great on paper, but I can't seem to get the leaf discs
to sink.  I've tried adding surfactant (i.e. Tween 80), changed from a
sink aspirator to a vacuum pump and nothing makes them sink!  One
suggestion I recently received is to use tobacco leaf material, I will
try this since I have been using Coleus, Spinach and Bean leaf discs.
If anyone uses this assay successfully in their lab please tell me your
secret to success.  Thanks so much!!
Andy Samuelsen


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