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 This is a continuously updated archive of the Aroid-L mailing list in a forum format - not an actual Forum. If you want to post, you will still need to register for the Aroid-L mailing list and send your postings by e-mail for moderation in the normal way.

  Duckweeds and Other Aquatic Aroids
From: Theodore Held <oppenhauser2001 at gmail.com> on 2009.01.20 at 15:48:32(18941)
Beth, and Others,

Duckweeds are certainly aroids that will grow in aquaria. Spirodella are easier to control, but are not quite so invincible as Wolffia or Lemna. In my experience, the smaller forms (Spirodella, alone excluded) are a royal nuisance. They tend to spread everywhere and are amazingly tough. One good thing, however, is that a single goldfish can clean up the whole mess in a few weeks or less.

The trouble with duckweeds, horticulturally, is that they have flowers so small that you'd be hard-pressed to find them or even see them, even if you look. Mostly what you see is a little glob of green, with or without a pitiful little root, possibly a pair of roots. None of these appearances are endearing to me.

One interesting feature of duckweeds and Pistia is that they are among the few species of aroid that can be seen easily from an airplane at 10,000 feet. I remember flying out from Miami after last fall's show and noting the big, uniform sheets of aroids floating tranquilly on inshore water. Very distinctive and far greener than any other massed plants. They are nearly luminous.

One thing I forgot to mention in yesterday's note on Pistia is that they are, size for size, one of the FUZZIEST plants I have ever seen. Challenge to the list: Is there another aroid that comes close to a Pistia for fuzziness? The leaf surfaces are covered with proportionally very long hairs of leaf tissue. Even the flowers are enclosed in spathes that look like tiny fur coats. This is one reason Pistia are so incredibly buoyant. Try to sink one and you will be amazed. Duckweeds, in contrast, are smooth and not nearly so unsinkable. In a closed glass container, the leaf hairs of Pistia condense water and create spherical water droplets perched delicately on leaf surfaces. In the "wild" Pistia will be found to be covered with these little jewels after a rain. In the current scientific lingo this effect is known as "water on a duck". But I think ducks cheat a little and have lightly oiled feathers. Pistia are the pure phenomenon: just a failure of water to sink down between the hairs and wet the leaf topology.

One other physical effect that may arise in Pistia stems from the fuzziness. That is, because of the huge surface area encompassed by the leaf hairs, I bet that transpirational water evaporation is likely extreme. The surface area of a mass of Pistia has got to be many multiples of the effective surface area of a similar patch of duckweed. Maybe this could be used for drying of flooded areas or other applications requiring huge evaporative strength. At the same time, the cooling effect of masses of Pistia and their evaporative water losses could be used as a form of "green" air conditioning. (?) Just a couple of speculations.

Ted.

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From: Walter Turner <wvturner at gmail.com> on 2009.01.23 at 10:05:04(18950)
Ted and others,

After reading your discussions, I was looking at the Wikipedia entry on Lemnaoideae. http://en.wikipedia.org/wiki/Lemnaoideae

Is this the current thinking? The article seems to have been written by someone knowledgeable, perhaps writing under the name Zeamays (I don't have enough experience with Wikipedia to be sure). Is that a member of our group?

Walter

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From: ExoticRainforest <Steve at ExoticRainforest.com> on 2009.01.23 at 18:17:24(18955)
Walter, I'm not familiar with thespecies so I can't comment there. However, many times I've found grosserrors on Wikipedia that appear to sound scientifically accurate. Idid some research on that "encyclopedia" and actually found that anyonecan post anything on Wikipedia and it is rarely edited unless byanother contributor who also may or may not have scientificbackground. I actually know of a teacher who did an experiment andedited a Wikipedia post on the brain just to see if anyone would changewhat she wrote and to this day her purposely false information is stillon the site (as far as I know)!

I research aroids almost every day of the year and constantly findmade-up or bad names on plants on that site all the time. Theinformation on there is often horribly wrong if compared to ascientific journal. As for me, I don't trust Wikipedia for much ofanything and always try to find other sources before even lookingsomething up on Wiki. I once edited a post on Wiki with a direct quote,word for word, from one of Dr. Croat's journals and it wasn't a weekuntil someone edited my post back to the way it was before. I gaveup!

There are so many "plant experts" out there that don't give a rip aboutscience, they only care about plant myths which is exactly why Istopped posting on UBC or any other plant discussion forum other thanAroid l. There is one guy on UBC who has made over 10,000 posts andwhen I bothered to read them I found bad info all the time. WheneverI'd ask for a source he'd point to A.B. Graf which any of the botanistson this forum will tell you his books Exotica and Tropica are filledwith errors. Mr. Graf's books haven't been edited for many years it isscary. But people often believe what he wrote above the scientfic infowritten by our most knowledgeable and gifted aroid botanists! If youuse Wiki, triple check the info!

Steve Lucas

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From: "Marek Argent" <abri1973 at wp.pl> on 2009.01.23 at 19:15:13(18956)
Everything is ok except the name - it should be Lemnoideae.

Marek

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From: Walter Turner <wvturner at gmail.com> on 2009.01.23 at 21:05:29(18958)
Marek, Steve, etc.:

I actually put "duckweed wiki" into Google and was automatically linked to the Wikipedia article I cited with the wrong spelling. And I did have to re-spell what I wrote there because I thought the wiki article would at least have the right spelling in the title! I knew it looked funny.

Steve, I do know how wiki works, but I have to admit that I too often accept what it says. It is one of those primrose paths, or whatever.

I take it from what Marek wrote that wiki is at least right, that lemna are under aroids. That the plants with the gigantic inflorescences and the smallest flowering plants are grouped together?

Walter

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From: "Marek Argent" <abri1973 at wp.pl> on 2009.01.25 at 17:54:52(18969)

Hello Walter,

The size doesn't matter :) The morphology of the inflorescence counts.

Here is the newest systematics of aroids (see attachments).

There are not all genera included, only the best known ones.

As I know the genus Rhektophyllum is now within Cercestis (or maybe I'm wrong)

I also don't know why Arisaema, Pistia and Alocasia are grouped together.

I don't remember from who I got these diagrams,

and I don't know on what criteria is it based (maybe on DNA?)

Marek

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From: Walter Turner <wvturner at gmail.com> on 2009.01.26 at 10:52:42(18985)
Thanks for these classification diagrams.

Walter

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