Inflorescence - Peduncle

[SKÁLA Zdeněk]

Well, several things seem to be mixed here. First, we should discriminate between the descriptive morphologic terms that are summarizing things looking alike ("berry") and comparative morphologic terms summarizing homologous things ("stem"). I do *not* like to start a thread about different homology concepts but still need to point that inflorescences need not be (mutually) homologous in any sense. Hence "inflorescence" is a descriptive morphologic term and, consequently, the same is true for "peduncle" that is defined by its position to an inflorescence. Generally speaking, peduncle is always a part of stem (and flowers within the inflorescence are homologous to other flowers) but it is a different level of description. Since the descriptive morphologic terms are a matter of convention (or of overall similarity) we can either include or exclude the peduncle in the inflorescence - we only should note it explicitly when starting a writing about it.

Best regards!
Zdenek Skala


-----Original Message-----
From: Guido Mathieu [mailto:guido.mathieu at TAXA.BE]
Sent: Tuesday, December 07, 2004 11:06 AM
To: TAXACOM at LISTSERV.NHM.KU.EDU
Subject: Re: Inflorescence - Peduncle


> Patrik Mraz wrote (off list and as part of a more elaborate text):
> Each hieraciologist knows "what is peduncle in Hieracium".

Also in Peperomia we know very well 'what' the peduncle is. And we know also
that it is of stem 'nature'. Were different opinions exist is to what 'spatial'
part of the plant it will be counted.
Anatomists e.g. state that it belongs to the 'spatial structure stem' because it
has its nature (according to such reasoning you have to consider the petals as
belonging to the leaves of the plant). Others state that an inflorescence has to
be seen as a 'functional' unit (with parts of different 'nature') and you have
to consider as belonging to that unit any part that contributes to the function.
Although plants seem to exist that develop solely peduncles until environmental
conditions are favourable (Websteria confervoides - Cypereaceae) this is
actually a deferred (normal) development and the presence of a peduncle only
make sense when other parts of the functional unit are also present. Still
others suggest to create a new term for this functional unit and to consider the
inflorescence as just the set of flowers within that unit.
Another (but related) consideration is that we have to be 'consistent' in our
concepts i.e. we have to use the same terms for homologous units. When one
agrees that the peduncle of a solitary flower is homologous to the peduncle of
an inflorescence (and not to the pedicel of one flower within that
inflorescence) one has to consider 'peduncle' part of the functional unit
'solitary flower' when he considers 'peduncle' part of the functional unit
'inflorescence'.

Guido Mathieu

Peperomia Research Group
Department of Biology
Ghent University
K.L. Ledeganckstraat 35,
B-9000 Gent. Belgium
www.peperomia.net