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  Some Botanical Fun
From: ted.held at us.henkel.com (ted.held at us.henkel.com) on 2007.10.23 at 09:58:25(16591)
Dear Friends of Botanical Curiosity,

There is an interesting article in the October 5, 2007 issue of Science
magazine entitled "Odor-Mediated Push-Pull Pollination in Cycads". The
reason I feel comfortable about sharing it to this list is that the
"push-pull" mechanism involves the warming of the cycad inflorescence and
the emission thereby of chemicals. Sounds like some aroids, no?

It seems they have a cycad in Australia called Macrozamia lucida and they
(especially the male) self-heat daily. This involves a temperature rise of
12 degrees C above ambient. This cycad is pollinated by a thrips (and some
of you thought thrips were solely placed on earth the vex horticulturists)
of a primitive thrips species called Cycadothrips chadwicki. During the
hours of 1100 and 1500 (11 in the morning to 3 in the afternoon) the male
plant heat up, emitting "male volatile emissions", which are attractive to
thrips in the absence of heat. Evidently, the warmed male odors are
obnoxious and/or toxic and drive the thrips, laden with pollen, out of the
male plant and toward the less-noxious female plant. The article states
that thrips that remain tend to die within ten minutes.

Once the heating cycle ends, the chemical activity and toxicity dissipates
and the odor reverts to being attractive to thrips again, whereupon the
thrips migrate back to the male cycad for another load of pollen. They
then discuss the specific chemicals and some experiments they did, which
may be less interesting to the general reader.

Finally, the article wraps up by observing "Floral scent may have
originally evolved to deter herbivores, and this system may represent a
conserved early intermediary in the evolution of seed plant pollination."
There are some interesting speculations there for the botanically- and
paleontologically-inclined.

For reasons I do not understand, the whole article can be read without
charge at the Science magazine site:

http://www.sciencemag.org/cgi/reprint/318/5847/70.pdf

They also claim to have a movie clip showing the mass exodus of thrips,
but I could not get it to download to my computer.

We tend to think of odor production in aroids as strictly attractive. But
I wonder if some repellency might also take place in order to force pollen
to another plant. Otherwise, why would a bug ever leave?

Ted.

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From: tindomul1of9 at yahoo.com (Tindomul Er-Murazor) on 2007.10.24 at 06:31:57(16600)
Thank you for the link. Their hypothesis seems plausible, but many times odors are put out to attract a certain sex of an insect species, where the males believe they are detecting the phermones of a female of their species and attempt to copulate with the flower "Pseudocopulation". I think it would be interesting to find out if the males leave because the flower changes its odor output or because the male realizes his error and then leaves.
Also, has anyone observed this in Amorphophallus or Symplocarpus? where pollinators leave the plant because they are repelled by it? On the other hand, there would be no reason to leave an aroid as most aroids carry both male and female flowers at different times and it would be advantageous to them to keep the insects on them at all times. Some even go as far as capturing their pollinators.

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From: ju-bo at msn.com (Julius Boos) on 2007.10.25 at 03:27:03(16607)
From: bogus@does.not.exist.com ()
Date: Tue, 23 Oct 2007 21:33:25 -0000
Subject: No subject
Message-ID:

Dear Ted,

Thanks for another very interesting and thought-provoking posting!
I recomend that those interested read Deni Bown`s WONDERFUL book "Aroids,
plants of the arum family".
Deni has an extensive section devoted to just this aspect of aroid
reproduction, the attracting of many genera and species of insects as
pollinators. The production of heat to disperse the attractive scents is
well documented in the Araceae, but Deni lists other plant families in which
this feature has been recorded-- the Annonaceae, Arecaceae,
Aristolochiaceae, Cycadaceae, Cyclanthaceae, and Nymphaeaceae.
To stick to 'our' plants, the aroids-- there are different 'strategies' used
by different genera to first attract, then "hold" the insects within the
bloom for the period necessary for fertilization of the female flowers, and
afterward to repel them when the male pollen is being produced so that they
can take this pollen away with them to another bloom that is at female
anthesis and so now is attractive to them, thereby achieving cross
pollination of one bloom by another bloom, hopefully of the same species!
The 'holding' method in some aroids is that they produce edible structures
or in some cases, secretions upon which the beetles actually stay and feed!
These structures are usually the sterile male florets, but other items may
be involved depending on the aroid. Sterile female florets, pollen,
nectar, etc. have been recorded.
The plant gives the insects enough time to (hopefully!) fertilize the female
flowers, and take note, my friends---this is no ''passive''
activity!!!--Deni describes an episode within the spathe of a Philodendron
bipinnatifidium as being "an orgy of mating and feasting on the nutritous
sterile flowers and secretions"!!! (and WE thought that ''we'' had invented
"night clubbing"!!)
When this sordid interlude is over-- all the available food has been eaten,
the beetles appetite for sex has abated (at least for a while!!), the flower
will begin male anthesis and producing pollen, and so several methods are
used to get the insects to leave, collecting pollen as they do so, and move
on to the next bloom (night club!!!!) at female anthesis. The food supply
may just run out, or the spathe may constrict and so leave little/no
comfortable 'space' for the insects, forcing them out. In other aroids the
upper portion of the spathe curves up and away, no longer forming a
protective 'roof' over the opening. Rain showers, a nightly occurence in
the tropics, cause water to then pour down into the spathe, so for the
insects, its leave QUICKLY or swim, or drown. With further research it just
might be discovered that there is in fact some sort of repellant factor at
work in certain aroids, who knows what mysteries are out there waiting to be
discovered and solved!
I encourage those of "us" who do not own the book by Deni Bown to get one
ASAP, you will NOT regret this decision, it is all (or at least most) of
what we NEED to know about aroids, and is certainly GREAT reading! [Thanks,
Deni!!!]
Lots more research is needed in this facet of 'our' plants lives!

The Best,

Julius

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From: bonaventure at optonline.net (bonaventure at optonline.net) on 2007.10.28 at 18:44:54(16621)
Wow, a potential thrip-repellent!
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