Inflorescence - Peduncle

[Guido at]

> 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