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Thu Jan 27 20:30:16 CET 2005

hardy  Aroids)" <ARISAEMA-L at NIC.SURFNET.NL> Aroids)" <ARISAEMA-L at NIC.SURFNET.NL>
Sender: "Arisaema Enthusiast Group (AEG) Discussion List (and other=
From: pbruggeman at TISCALI.NL
Subject: Betr: Re: Arisaema dilatatum germination quandary
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Adam,

I have given it some thought but that's about it, analyzing is a big word==
.....
This type of germination occurs in several sections and following the cur==
rent
treatment of the genus on a sectional level, there are several sections t==
hat
have species with both hypogeal and epigeal germination. If one sees the
sections as a reflection of evolutionary relationships then the type of g==
ermination,
hypogeal or epigeal, seems of little relevance if both types occur in the==

same section. Following along that line, the fact that several species fr==
om
different sections show this type of germination suggests that each speci==
es
has developed this type of germination independantly (converging evolutio==
n).
That does not mean related species that show the same gemination type hav==
e
developed that independently, it could be a trait inherited from a common==

ancestor.

The fact that old seeds of A. nepenthoides sometimes show both epigeal an==
d
hypogeal germination suggests that it could be caused by ecological circu==
mstances
because older seeds that take more time to germinate are aware that by th==
e
time they produce a seedleaf, the growing season might be over.  How one
proves such a hypothesis, I don't know. It should be of some benefit for
the the species in question and to me, ecological circumstances seem the
most likely ones.

My remark on the use of the word "protocorm" by Murata and Guy was only m==
eant
to show that the structure of the small bulblike structures formed by Ari==
saema
seems different from the  true protocorm orchids develop. Orchid protocor==
ms
have a specific tissue that enables it to interact with fungi wheras the
bulk of the orchid protocorm consits of undifferentiated cells. Clearly A==
risaema
"protocorms" are not like that. One of the reasons orchids need to intera==
ct
with fungi is that the seedbody needs to take up certain nutrients to pro==
duce
a seedleaf which it can't do on its own. It would really surprise if that==

were the case with the hypogeal Arisaema but because so little is known a==
bout
this phenomenon, no explanation can be excluded beforehand. What it shoul==
d
be called I have no idea, what is it called in Lilium?

How far the distance of the young tuberlet is from the original seed is n==
eglicible
if one looks at some Arisaema species like tortuosum which can end up 3-4==

cm deeper than the sowing depth at the end of the season. To my knowledge==

the initial phase of germination is the same for both epigeal and hypogea==
l
species, they only seem to differ in the fact that epigeal species form a==

first root and seedleaf. Hypogeal species lagerly remain undifferentiated==

but very soon do have a growing tip and sometimes a root tip from which t==
he
roots will develop the second season.That doesn't mean it waits for the s==
econd
season and does nothing. It increases in size and the root tip and first
bud get more pronounced.

Pascal

>-- Oorspronkelijk bericht --
>Date:         Thu, 27 Jan 2005 11:02:11 -0600
>Reply-To:     "Arisaema Enthusiast Group (AEG) Discussion List (and othe==
r
>hardy              Aroids)" <ARISAEMA-L at NIC.SURFNET.NL>
>From:         Adam Fikso <irisman at AMERITECH.NET>
>To:           ARISAEMA-L at NIC.SURFNET.NL
>Subject: Re: Arisaema dilatatum germination quandary
>
>
>Good Morning,  Pascal,  Thanks for your extended response.  I understood==

>"trade" to be "trait"--I had no trouble with it, just read it with a Dut==
ch
>accent, and it made sense.
>
>Because of my fingers (too big and clumsy) and eyes, (lack of binocular
>convergence), I have to proofread everything and still miss some of my
>errors.
>
>I note that we again have this group's communication button turned to th==
e
>"ON" position , maybe because even though the exchange is not, strictly
>speaking, an arisaema matter, it is relevant, interesting, and when ther==
e's
>snow and ice on the ground, something worth doing.  I know that I learn
from
>it, because I can't find everyting on the Internet, not even from  Botan==
y
>on
>Line.
>
>
>
>
>
>
>  It therefore might be influenced by ecological
>circumstances which would make the production of the seedleaf unfavourab==
le
>in the first year.
>
>This occurred to me as something that might be true in the species' hist==
ory
>
>
> One might think, for instance, that high altitude species
>with a relatively short growing season, would prefer this type of
>germination
>more but I have tried to analyze the species that show this type of
>germination
>and the habitat they come from and thusfar I have not been able to make
any
>correlation.
>
> But you analyzed it
>
>It seems to occur random throughout the genus and, at best,
>would suggest it is a trade aquired by species independant from one anot==
her
>(convergent evolution) in a similar way that members of section Tortuosa==

>all have the same spadix appendix type but do not all seem to have the s==
ame
>ancestor. The species that do show a certain characteristic can be relat==
ed
>to eachother but only because the common ancestor has developed the trad==
e.
>The possibility of this type of germination is there but only few actual==
ly
>have developed it.
>
>As I noted above, I was thinking of a hypothetical common ancestor
>
>Also what the small tuber is is hard to say. The use of the term "protoc==
orm"
>is strictly speaking false
>
>OK, But what else should one call it ?
>
>because that only applies to the relatively unstructured
>mass of cells formed by orchids after germination that have interaction
with
>mycorrhiza.
>
>
>There seems to be some structure in the small Arisaema tubers
>and usually the size of the little tuber at the the end of the first sea==
son
>is twice the size of the initial seed but can they already take up nutri==
ents
>without photosynthesis?
>
>
>I would not be too sure  that there is NO photosynthesis.  I recall some==

>experiments many years ago, but cannot recall a reference  (not even in
my
>own field for some things)  which showed that light could be detected as==

>far
>down as a couple of inches in the soil, depending, of course on the
>structure.   In loose leaf litter, there might be quite a bit of light
>available to a germinating seed, and one should not forget the possible
>effect of symbiotic organisms assisting in germination, e.g., aspergillu==
s
>in
>seeds of some palms.
>
>    Would it be an advantage to store nutrients the first
>year and produce bigger growth the next year?
>
> Of course this seems reasonable.
>
>It definitely is not meant
>to place the young tuber deeper in the soil because the roots formed by
>species
>that produce a seedleaf in the first season do that job much better than==

>the distance the young tuber   is formed away form the initial seed.
>
>How big a distance is this, say, in diameters of the seed?  I've never s==
een
>it , so would like to know, "just to send it around in the roulette whee==
l
>of
>my mind"    <:-)  (pointy-headed intellectual theorizing type) Regards,
Adam
>
>
>
>
>
> Fascinating
>stuff but I am afraid more questions than answers.
>
>There are always more questions than answers:  and  this provides us
>direction for observations.  Regards, Adam
>
>
>
>Pascal
>>-- Oorspronkelijk bericht --
>>Date:         Wed, 26 Jan 2005 18:04:15 -0600
>>Reply-To:     "Arisaema Enthusiast Group (AEG) Discussion List (and oth==
er
>>hardy              Aroids)" <ARISAEMA-L at NIC.SURFNET.NL>

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