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Re: flowering 'juvenilies'

  • To: Multiple recipients of list AROID-L <aroid-l@mobot.org>
  • Subject: Re: flowering 'juvenilies'
  • From: "Eduardo Goncalves" <edggon@hotmail.com>
  • Date: Thu, 15 Jun 2000 21:41:04 -0500 (CDT)

Dear Aroiders,

    The production of sexual parts in juvenile individuals is a
morphogenetic "accident", but it is usually explored by the evolutionary
history of many groups. There are two morphogenetic processes associated to
this aspect: Paedomorphosis and Neoteny. Both concern juvenile individuals
with mature sexual parts or juvenile structures that are kept active in
adult individuals. These phenomenons occur in both plants and animals. Some
evolutionists say that humans are just neotenic apes, because our brain
continues to develop for a long time after birth! Anyhow, theses processes
are also know in plants and maybe they are a good natural method to "make"
new species. Juvenile (or poorly diferenciated) organs are usually very
plastic and can adapt to different conditions. If this ability to be
morphologically plastic is important for the effective survival of a quoted
species, it can be kept or even "improved" by natural selection.
     I have one possible example. One of the most morphologically variable
genus in the tribe Spathicarpeae is Spathicarpa. It is small, with poorly
differenciated ground tissues and have usually the simplest leaf type in the
tribe (I mean the same type we find in seedlings of almost all  genera of
the tribe). One of my hypothesis (still in test) is that Spathicarpa is a
neotenic genus in Spathicarpeae. The same for Urospathella wurdackii
G.S.Bunting (now currently recognized as Urospatha wurdackii (G.S.Bunting)
Hay). It is a Urospatha that flowers with the leaves of seedlings!!!!  Maybe
this kind of leaf is useful in those savannas this species occurs. Or maybe
it is just an accident that soon will be erased by natural selection!
     In the case of the supposed M. dubia that flowers with juvenile
flowers, we can make some free speculation about this. In the "normal"
environment of the species, maybe it is not a good idea flowering this way,
because pollinators may not be able to find the flowers. Meanwhile, if this
plant spread to new areas, maybe with smaller trees and different potential
pollinators, it can prove to be successful (in evolutionary aspects), so it
can diverge from the main species and become ANOTHER species. If evolution
can be so creative than me (I don't think so), it is really possible to
occur in nature!

                I hope you enjoy those crazy ideas!!  :o)


>From: "Peter Boyce" <p.boyce@rbgkew.org.uk>
>Reply-To: aroid-l@mobot.org
>To: Multiple recipients of list AROID-L <aroid-l@mobot.org>
>Subject: flowering 'juvenilies'
>Date: Thu, 15 Jun 2000 16:45:43 -0500 (CDT)
>Dear All
>The newly raised issue of juvenile monsteroids flowering is
>interesting because, while the production of flowers by a plant
>vegetatively in a juvenile phase does occur in the monsteroids,
>notably Monstera tuberculata, Rhaphidophora hayi, R. latevaginata,
>R. pachyphylla, R. parvifolia, R. okapensis and Scindapsus lucens,
>this 'M. dubia' thing is that the plants are flowering with very small
>leaves and BENEATH the leaves, whereas in all of those listed
>above while the juvenile growth morphology is retained into
>flowering in most instances the leaves of flowering individuals are
>considerably larger than those of youngsters and the
>inflorescences are carried clear of the leaves either at the tips of
>clinging shoots or on free shoots arising from the leaf axils. If the
>description of this 'dubia' plant is correct it would appear that
>inflorescences are arising directly from the leaf axils. Because
>aroids ALWAYS flower at the shoot apex it would mean that in this
>plant each inflorescence is carried at the tip of a very short shoot
>arising in the leaf axil (the same situation as in Pothos scandens) -
>a feature not yet recorded in the Monstereae.
>Peter Boyce
>Royal Botanic Gardens, Kew
>Richmond, Surrey
>TW9 3AE
>Tel. (+44) (0)20 8 332 5207
>fax. (+44) (0)20 8 332 5278
>email: p.boyce@rbgkew.org.uk (work)
>        boyce@pothos.demon.co.uk (home)

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