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Re: Some Botanical Fun

  • Subject: Re: Some Botanical Fun
  • From: "Julius Boos" <ju-bo@msn.com>
  • Date: Thu, 25 Oct 2007 10:27:03 +0000

>From : 	<ted.held@us.henkel.com>
Reply-To : 	Discussion of aroids <aroid-l@gizmoworks.com>
Sent : 	Tuesday, October 23, 2007 4:58 PM
To : 	Discussion of aroids <aroid-l@gizmoworks.com>
Subject : 	[Aroid-l] Some Botanical Fun

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, 
Lots more research is needed in this facet of 'our' plants lives!

The Best,


>>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 
plants 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 

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


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?



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