Help on plant hormones labs

Bill Williams bwilliam at
Fri Oct 28 09:40:20 EST 1994

Plant People,

We have been using a "chemical control in plants" lab for a few years
now that supposedly illustrates the role of auxin in gravitropism in
shoots.  Never mind that the role of this hormone in shoot gravitropism
is now highly questionable, the point is the damn thing doesn't work! 
Here's what we were doing:

1.  Take a quad of fast plants.
2.  De-capitate three of the plants in the quad.
3.  Leave one untreated, treat one with lanoline paste, treat the other
with lanoline past containing IAA.
4.  Put the quads on their sides in the dark for a couple of hours.

5.  We also do an exercise on mobilization of starch in barley seeds as
stimulated by GA, and stimulation of adventitious roots by NAA.  Both
of these work quite well.


1.  The IAA only seems to work some of the time, and very unreliably.
2.  Just this semester, even the non-decapitated controls took FOREVER
to bend up the requisite 90 degrees.


Can someone suggest a different exercise to demonstrate the elongation
effect of IAA?  Have any of you tried making tiny agar blocks and
repeating Fritz Went's stuff, in an undergraduate lab setting?  How
about other coleoptile-oriented exercises?  
Bill Williams
bwilliam at
Dept. of Biology
St. Mary's College of Maryland

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