clarification of phyllotaxis

Ross Koning koning at ECSUC.CTSTATEU.EDU
Fri Nov 21 09:33:37 EST 1997

At 6:55 PM -0500 11/20/97, Grant R. Cramer wrote:
>Hi all,
> I am hoping one of you can enlighten an ignorant soul. I have been
>teaching my class about phyllotaxis using  the text "Botany' by Moore et
>al. They define phyllotaxis as the number of turns of a spiral/number of
>leaves BETWEEN successive leaves of an orthostichy. As I went to expand on
>this subject by giving an example from Esau's "Anatomy of Seed Plants", I
>discovered that she describes 5/13 phyllotaxy as "five windings about the
>axis include 13 leaves with leaves n and n plus 13 located one above the
>other". That is there are only 12 leaves BETWEEN successive leaves of the
>orthostichy. These two definitions are slightly different but important.
>The other surprise was that the phyllotaxis was 5/13 not 8/13, which is
>what I expected based on the Fibonacci series and how it is explained in
>Moore et al.
>My question is "What is the correct definition of phyllotaxis" or is there
>no agreement on this?


My understanding and experience tell me that Esau
is giving you the right answer and I think Moore
is intending to say the same. I have my students
grow mystery plants (seeds supplied in a plain-
brown envelope) and to write a term report on
their investigations on the anatomy, morphology,
and physiology of their plant species.  These
reports often include phyllotaxy and several have
asked me to help them understand it.  All plants
I have examined this way fit the quote you mention
from Esau.  Many of the plants I have examined have
had the 5/13 phyllotaxis.  Both 5 and 13 are part
of the Fibonacci series, so this arrangement meets
expectations.  The two numbers do not have to be
adjacent elements in the series as far as I know,
and my experience agrees with that.


Ross Koning                 | koning at
Biology Department          |
Eastern CT State University | phone: 860-465-5327
Willimantic, CT 06226 USA   | fax: 860-465-4479

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