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  self pollination of aroids
From: "zach" r2ot at charter.net> on 2003.05.12 at 12:45:50(10246)
hello

does anyone here know which genera of tuberous aroids
can and can not be self pollinated succesfully?

zach

From: Marc Gibernau gibernau at cict.fr> on 2003.05.13 at 01:13:11(10248)
Dear Zach,

Aroids is a big family with great variability.
Due to the protogyny, self-pollination is not supposed to be common (but
several taxa have overlapping stigma receptivity and pollen release).
Arisarum vulgare can be self-pollinated, if you brush the stigma with a
paintbrush.

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From: "Julius Boos" ju-bo at msn.com> on 2003.05.18 at 05:27:50(10266)
Dear Zack, Marc and Friends,

I have a couple observations and comments on this subject-- in Urospatha
the female and then the male anthesis are very obvious (as I noted in my
notes on this genus in Aroideana), the female anthesis takes place just as
the spathe begins to open, and drops of liquid will be observed on the
stigmas. This phase lasts several days, then the tips of the stigmas turn
brown and dry up. Soon after the female phase is completed, the strands of pollen can then be observed being produced, starting
at the very TOP of the spadix and slowly working downward the entire length, and
this phase can take a week to ten days or more. Because these two phases take place
pretty far apart and with no apparent 'overlap', and the female stigmas are dry when the pollen is being
shed, I do not believe self-pollination can take place. But---on a large
mature plant just a very few fruit will still develop and contain some viable
seed without apparent pollination , even if there is only one bloom on a single plant in your collection. Small or immature plants will generally abort the bloom with no fruit/seed production, and (as I have suggested previously) perhaps only make their contribution to genitic diversity by their pollen production. I discussed this with the late Dr. Birdsey, he explained that this seed production without pollination is called 'apomixis', and is not self-pollination. Recently I have seen a Xanthosoma acutum
Goncalves (section Acontias, a tuberous sp. like most Caladium sps.) develop
a full infructesence with only one bloom present, and since this genus also
has distinct non-overlapping (as far as we know) female then male anthesis, we suspect apomixis in at least this species in the genus Xanthosoma.
I have been pondering the possible 'benefit' of apomixis vs. true self-pollination, and wonder if my thoughts bear merit---we are told that self-pollination is not a 'good' thing because of the non-transference of genetic material between two different plants, so we accept this, and so I wonder how apomixis may 'benefit' a plant. I was thinking----suppose a single seed, transported by a bird or other means, falls on fertile ground and grows into an adult and flowering plant, but too far removed from another plant or population to allow for cross-pollination. The plant blooms, and a few seed are produced by apomixis which fall and grow near to the single parent plant, these plants are clones of the 'mother' plant, but we should bear in mind that in her seed she carries the genes of her parents and the plants that produced 'her'. When a bloom from this population of clones is pollinated by another related clone, there is more mixing of genetic material than would occur if there were true self-pollin
ation (but less than if there were cross-pollination by an unrelated plant), so eventually this may allow this population that were originally clones by apomixis to become a self-sustaining and sufficiently diverse in genetic material to be healthy population, as soon there will be sufficient plants in this new population to allow cross pollination to begin.
Any comments??

Julius

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From: Marc Gibernau gibernau at cict.fr> on 2003.05.19 at 06:49:29(10270)
Dear Julius, and Friends,

I have many comments on your last message.

You are right Julius, there are two phenomena :
self-pollination, that is the fertilization of ovules by its own pollen
that will consequently lead to the formation of seeds.
Apomixis that will lead to the formation of (viable) seeds without any
fertilization (e.g. no pollen needed) by ?parthenogenesis/parthenocarpy? of
some cells (you have about 10 kinds of apomixis according to the kind of
cells implied: egg-cell, endosperm,?).

In the first case, two genetic informations are mixed whereas in the second
just one genetic information is duplicate.

As you mention for Urospatha and Xanthosoma acutum, may not present
self-pollination as you observe that protogyny is complete (no overlap).
Then apomixis is certainly present in these taxa. The best way to test it
(without counting chromosomes) is to castrate (part of) inflorescences to
see if just female flowers can produce seeds. In my recent study of
Montrichardia (for those interested see attached file), I observe that
bagged inflorescences produced seeds, but I was not able to distinguish
between self-pollination and apomixis. Such answer needs a specific
experiments.

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From: "Michael Marcotrigiano" mmarcotr at email.smith.edu> on 2003.05.19 at 12:18:48(10272)
It is important not to confuse apomixis (embryo produced without
pollination - so a clonal seed source) from parthenocarpic - fruit
forming without seed = no reproduction)

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From: "Julius Boos" ju-bo at msn.com> on 2003.05.20 at 02:12:39(10274)
Thanks for the comment! In the genus Urospatha there seems to be true
apomixis, as there are only a very few fruit produced on a spadix that has
not been pollinated, and these fruit generally contain less that their full
'quota' of seeds, but there are viable seed produced in most of the few
fruit, thereby continuing the reproductive process without cross or self
pollination.

Julius

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From: "Julius Boos" ju-bo at msn.com> on 2003.05.20 at 02:28:30(10275)
Dear Marc and Friends,

Thank you for your most informative and interesting comments! I think we
both agree completely without realizing it! I am not an expert on these
matters, but was trying to determine/illustrate that apomixis was at least
as good and perhaps better than self-pollination, as perhaps there was more
and different genetic material available in apomixis for continued and later
cross-pollination in a population of plants that were started by just one
good seed originally produced from cross-pollination, but growing all by
itself in a remote area. I thought that perhaps reproduction by apomixis
(vs. cross-pollination) until there were a few plants in this new population
to enable cross-pollination to begin may be 'the better of two evils' as it
were, but obviously not as 'good' as cross-pollination in a large and
thereby very genetically variable population.

Julius

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From: MossyTrail at cs.com on 2003.05.20 at 20:40:40(10276)
"Julius Boos" wrote:

>
>Dear Marc and Friends,
>
>perhaps there was more
>and different genetic material available in apomixis for continued and later
>cross-pollination in a population of plants that were started by just one
>good seed originally produced from cross-pollination, but growing all by
>itself in a remote area. ? ?I thought that perhaps reproduction by apomixis
>(vs. cross-pollination) until there were a few plants in this new population
>to enable cross-pollination to begin may be 'the better of two evils' as it
>were, but obviously not as 'good' as cross-pollination in a large and
>thereby very genetically variable population.

I presume you are referring to heterozygousness (heterozygosity?); that is, your one single plant has two forms of an allele. Then, when it self-pollinates, the alleles may be recombined to produce previously-hidden diversity. Sorry, I am having trouble expressing myself clearly tonite.

Jason Hernandez

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From: Marc Gibernau gibernau at cict.fr> on 2003.05.21 at 00:38:53(10277)
Dear Julius, Jason & Friends,

Apomixis do not produce more and different genetic material as all the
seeds are identitical as their mother, they are all clone but instead of
being bulbils,... they are seeds. So if the mother was genetically variable
(heterozygosite) its offspring will also be...
This way of reproduction is like a clonal reproduction that leads to the
formation of seeds (with the advantage/disadvantage of been dispersed: new
habitat colonization suitable or not!!!).

Apomixis in general does not prevent from been cross-pollinated, as Julius
mentioned this "breeding system" can operate when sexual partners are
lacking later if the population grows apomixis can co-exist or be replaced
by cross-pollination.

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From: Marc Gibernau gibernau at cict.fr> on 2003.05.21 at 04:49:54(10278)
Dear Julius & Friends,

I listed the advantages and disadvantages of apomixis in a previous e-mail.
So it will depend on the populational state of your species.

If I understand well your question, apomixis will never "mix" genes (it's a
cloning multiplication better than reproduction). But apomixis will "keep"
all the genes in place (for future mixing if cross-pollination occurs).

Self-pollination will mix the genes and all lethal genetic combinations
will be

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From: Marc Gibernau gibernau at cict.fr> on 2003.05.26 at 01:14:50(10289)
Dear Julius,

No problem, It has been a pleasure to discuss with you and others.
I agree with your last message about population founding and apomixis
advantages in this case. Of course it would be very interesting to look
closely at these phenomena in Urospatha and Lasioids. May be one day....

All the best,

Marc

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