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Pistil versus carpel

David W. Kramer kramer.8 at OSU.EDU
Mon Aug 26 08:58:40 EST 1996

David Hershey asks:  "Current intro. college botany textbooks seem split on
the definition of pistil. Some stick to the traditional definition that a
pistil is composed
of one or more carpels. Others consider pistil and carpel to be synonyns.
Two books do not even list pistil in their index and seem to want to phase
it out. If there any justification for changing the definition of pistil
after so many years?"

There is a clear need for keeping the two terms, carpel and pistil.  They
are not synonymous except in the case of the simple pistil, composed of a
single carpel.

In plant taxonomy it is important for students to understand the
distinction.  Frequently families are defined by the number of carpels in
the pistil.  The way the carpels are fused is a clue to relationships at
the genus or family level.

The fact that one term or the other is left out of certain textbooks merely
reflects a judgement on the author's part about the amount of detail to
introduce for the intended audience.  I certainly would not recommend
teaching young children about carpels.  It is sufficient for their purposes
to learn pistil.  I teach my students the distinction in our Introduction
to Plant Biology, a non-majors course.  It isn't simply a matter of
memorizing a definition... I deal with this in the context of discussing
the evolution of flowers.  Flower evolution is one of the evidentiary bases
we establish for a later discussion of the principles of evolution.

The easiest way to teach the concept of carpel is to start with the pea pod
(nearly always available for dissection at the local supermarket) which, as
you know, is a simple pistil, composed of a single carpel.  Students can
easily cut open the pea pod and fold it back to show the leaf-like nature
of the carpel, with ovules attached at the margins of the leaf.  Then I
suggest that they take five pea pods and bundle them together with a rubber
band to simulate fusion.  Then we notice the kinds of "clues" one can look
for to determine carpel number in a pistil/fruit:  number of "scallops" on
the ovary, number of style/stigma branches, and number of locules in the
ovary.  The students have no trouble remembering the concept after that
"hands-on" exercise.

Dr. David W. Kramer
Department of Plant Biology
Ohio State University at Mansfield
1680 University Drive
Mansfield, OH  44906
(419) 755-4344  FAX:  (419) 755-4367
e-mail:  kramer.8 at osu.edu

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