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Re: flowering 'juvenilies'


>Date: Fri, 16 Jun 2000 19:25:30 -0500 (CDT)
>Reply-To: webmaster@plantapalm.com
>Originator: aroid-l@mobot.org
>Sender: aroid-l@mobot.org
>Precedence: bulk
>From: Jody Haynes <webmaster@plantapalm.com>
>To: aroid-owner@mobot.org
>Subject: Re: flowering 'juvenilies'
>MIME-Version: 1.0
>
>This message was submitted by Jody Haynes <webmaster@plantapalm.com> to list
>aroid-l@mobot.org. If you forward it back to the list, it will be distributed
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>
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>should be able to do so by simply replying to this note.
>
>----------------------- Message requiring your approval ----------------------
>Sender: Jody Haynes <webmaster@plantapalm.com>
>Subject: Re: flowering 'juvenilies'
>
>Eduardo,
>Yours was an interesting post. I, too, have some knowledge (and an astute
>interest) of paedomorphosis and neoteny--but only in animals. I was not
>aware of
>the process in plants.
>
>I feel that these terms should be clarified. Although they both refer to the
>"possession in the adult stage of features typical of the juvenile stage
>of the
>organism's ancestor", neoteny specifically refers to sexual maturation of the
>'juvenile' stage: "heterochronic evolution whereby development of some or all
>somatic features is retarded relative to sexual maturation, resulting in
>sexually mature individuals with juvenile features" (Futuyma, D. J. 1986.
>Evolutionary Biology. Sinauer Associates, Inc. Sunderland, MA.).
>
>Thus, paedomorphosis refers to the simple possession of juvenile traits in an
>adult organism, but does not specify a process; conversely, neoteny is the
>process by which somatic maturation is retarded relative to sexual maturation.
>
>Does this make sense? Anyone else care to comment on this interesting topic?
>Jody
>--
>Jody Haynes
>Corresponding Secretary, Editor & Webmaster
>Palm & Cycad Societies of Florida (PACSOF)
>  Virtual Palm & Cycad Encyclopedias
>  Website: <http://www.plantapalm.com>
>              &
>Seedbank Facilitator, Webmaster & List Owner
>Azafady Madagascar Seedbank
>  Website: <http://www.azafady.org>
>  E-mail List: <madagascarseed@egroups.com>
>
>Eduardo Goncalves wrote:
>
>> 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)
>>
>>                                         Eduardo.
>>
>> >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.
>> >
>> >Pete
>> >
>> >----------------------------
>> >Peter Boyce
>> >Herbarium
>> >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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