Hormone Absorption

David W. Kramer kramer.8 at OSU.EDU
Fri Nov 19 13:04:24 EST 1999


In our PB101 Introductory Plant Biology course for non-majors the students
do an experiment with dwarf and normal garden peas.  They plant both then
treat dwarfs with gibberellic acid (GA) to see if they will grow as tall as
normal, untreated peas.  They grow the appropriate control plants, too.
They apply the GA with artist brushes by brushing the solution on leaves
and stems.  The experiment always "works"!

Now a student has asked why we don't put the hormone solution (0.20 gms
GA/liter dH2O) on the soil instead of painting it on.  The simple but
unsatisfactory answer is that "we've always done it that way!"  Would we
get the same effect if we "watered" the plants with the GA solution,
applying it to the soil?  [I'll try this next quarter but thought some of
you might have the answer!]

How do the pea plants actually absorb the GA?  The stems and leaves have a
heavy cuticle so I assume it enters via stomata on the leaves and stems but
what then?  Does it enter cells by active transport? simple diffusion? some
other mechanism?  Is it transported in the xylem or phloem or by other
cells?

While we're at it, do you know how chrysanthemum cuttings absorb the
napthaleneacetamide from Rootone?

OK.  Now you know I'm not a plant physiologist!  Help!
*********************
David W. Kramer, Ph.D.
Asst. Prof. of Evolution, Ecology, and Organismal Biology
Ohio State University at Mansfield
1680 University Drive
Mansfield, OH  44906-1547
Phone:  (419) 755-4344      FAX:  (419) 755-4367
e-mail:  kramer.8 at osu.edu




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