"Jay Vannini" on 05/20/2000 11:15:57 AM
Please respond to aroid-l@mobot.org
To: Multiple recipients of list AROID-L
cc: (bcc: Bonaventure W Magrys/ADM/SHU)
Subject: Re: secondary hemiepiphytes
Alan:
As a lay observer, I don't pretend to have an answer to your question, but
rather will pose another related one - that is - do these "hemiepiphytic"
aroids always dispense with soil root systems once airborne elsewhere in the
Neotropics?
Sorry to jump in so late here with my two centavos worth, but it is my
observation that several of the large scandent aroids that are native to
northern Central America commonly continue with very visible links to the
ground, even as they pursue the good life in the upper canopy. I have
recently examined a vigorous wild population of the species that you first
mentioned (Monstera deliciosa) in premontane wet forest near that Chiapan
border and, offhand, I remember that many of the plants I saw could be
traced back down to the ground down very robust host-clasping stems. This
was also evident in mature Monstera friedrichsthalii, Syngonium steyermarki
(ID?) and a very large Philodendron sp. seen in the same region.
Again, this is only my opinion from admittedly casual observation, but it
seems to me that while these plants CAN readily dispense with ties to the
soil, they don't necessarily have to do so. Therefore, this event seems more
an adaptation to accidental (?) loss of the original root system - clearly
an advantage to plants whose fates would otherwise be tied to that of their
hosts following its death. As anyone who has visited an old light gap caused
by a tree fall in humid tropical forests in this region can attest, many
mature vines attached to fallen trees have often just reverted back to the
juvenile climbing stage and headed for the nearest handy trunk to
re-colonize.
Perhaps we shud refer to this regenerative phase as "phytopragmatism" (just
kidding).
Amongst several other groups of plants that I am familiar with, there are
indeed clear parallels to this habit in some aroids. Several of the larger
"highland" Nepenthes pitcher plants from tropical Asia, most notably N.
lowii and N. pilosa, often part from old, rotting basal stems and continue
to grow and reproduce as epiphytic canopy vines. Likewise, many cereoid
cacti inhabiting moist tropical habitats, esp. Selenicereus testudo,
Hylocereus spp. and Werckleocereus spp. also do this on a regular basis.
Again, this appears to be an adaptive response by succulent-stemmed climbers
to environments conducive to loss of basal stems and roots due to fungal,
bacterial and insect attack over the relatively long life of the plant.
Your questions do open an interesting avenue of research, that is, how
common is this ability in tropical climbers and what species do
"voluntarily" cut ties to the ground, and why. There are a number of
individuals that attend this forum that are familiar with regions with far
higher epiphyte diversity than Guatemala and Mexico; perhaps they will share
their views on this subject.
Best of luck with your project,
Jay Vannini
----- Original Message -----
To: "Multiple recipients of list AROID-L"
Sent: Friday, May 19, 2000 10:26 PM
Subject: Re: secondary hemiepiphytes
> ok, cool. Thanks to those who gave answers.
>
> I note though that most explanations focus on why a plant would want to
> get to the canopy area, as opposed to why it would elect to GET RID of
> the underlying stem. One writer, who wrote by email, noted that this may
> be simply the result of cumulative damage to the lower (and older)
> regions of the plant. Although this may be possible, my understanding is
> that the degradation is too drastic to be simply due to random
> accidental events, and it of course does not address why this would
> occur in several diffrent groupings of plants while not in most others.
> Indeed, I once observed a large PHilodendron in a greenhouse which clung
> only 1.5 meters or so above the ground...its old pot lay forlornly below
> it....
>
> Another notes that adventitious roots could make up for the loss of a
> stable water supply, but then notes that conditions even in rainforst
> areas up in the canopy is relatively different from one time to another
> and from even one tree area to another. Many plants (I think) do not
> dispense with their ground roots, while these MOnsteras and
> PHilodendrons do....
>
> What characteristics do these plants and similar others have that differ
> from other vinelike plants that start at ground level but never
> relinquish their hold on earth? Is this a competitive advantage that
> allows these plants to compete equally against others in similar niche
> (well, you may have a stable water supply, but you gotta spend energy
> maintaining it, whereas ther is a chance I may end up in an inhospitable
> spot, but in the meantime, I can recycle old tissue matter into growing
> at the tips, and growing faster than you)...
>
>
> anyways, thanks for the answers.
> alan in New Jersey, USA
>
>
>
>
|
IAS on Facebook
IAS on Instagram
