Inflorescence - Peduncle

[Richard Jensen]

"Thomas G. Lammers" wrote:

> At 07:49 AM 12/6/2004, Richard Jensen wrote:
>
> >Seems to me it matters a lot.  Not all stems develop into inflorescences.
>
> Well, fair enough.  But the point remains, it *is* a stem, not a root or
> leaf, and not something sui generis.

In that case, then the rachilla of a grass spikelet is a stem and the gynophore
in Cleome might just as easily be called a stem.

>
>
> >In some inflorescences the peduncle is part of a very well defined unit,
> >e.g., the catkins of Quercus.  However, in other cases there is what
> >appears to be a gradual transition from stem to peduncle, e,g, in Solidago
> >caesia
>
> But does that reflect some biological reality or just human
> perception?   Substantively, the only hard and fast difference I see
> between the two is the presence of (I assume) an abscission layer that
> allows the oak catkin to be "jettisoned" from the branch.  Otherwise, both
> are stems bearing leaves and flowers in their axils.

The catkins of oaks do not have "leaves," although some have "bracts."  And,
this is the heart of the question - is it it just human perception or does the
concept of peduncle reflect some biological reality.

> I prefer to keep it loose -- "a collection of flowers" -- and then deal
> with specifics of the stems, leaves, and flowers making it up.
> Thomas G. Lammers, Ph.D.
>

But that's what's being asked - what are the specifics?  From the standpoint of
organography, this becomes an important matter.  Do we claim that the male
inflorescence of a walnut is homologous with the male inflorescence of an oak?
Is an ear of maize homologous to a head of wheat?  Curious botanists want to
know!

Cheers,

Dick
--
Richard J. Jensen              | tel: 574-284-4674
Department of Biology      | fax: 574-284-4716
Saint Mary's College         | e-mail: rjensen at saintmarys.edu
Notre Dame, IN 46556    | http://www.saintmarys.edu/~rjensen