Allelochemicals, roots and competition

> From: Stephen.Pushak at saudan_HAC.COM
> Date: Thu, 21 Sep 95 18:03:25 PDT
> Subject: Re: Allelochemicals, roots and competition

> Yet A. mad. will
> continue to show very slow growth even with trimming back the
> neighbours. 

I'm not at all sure that what you are seeing in this case is 

> Some even suggested that Crypts and this Aponogeton
> had an affinity; increased oxygenation due to the roots of the
> neighbour.

Although it is possible that increased oxygenation (or 
circulation) is beneficial to A. mad.,(it certainly seems to be to 
other rooted plants) it seems unlikely that this is a Cryptocoryne 
specific phenomenon.  They don't even come from the same 
continent, so this would be a strange adaptation, indeed. ;-)

> For the Madagascar Lace plant we've got to focus on that individ
> since its demands seem so exact and unfortunately, unknown. 

I agree with you completely here.  In fact, I have read several 
reports of success where the plants were kept either as a single 
specimen, completely by itself, or else in a monoculture.

> John Madesen wrote:
> > I am replying to  the comment about rooted plants outcompeting
> > for nutrients.  Scientifically, there is no good basis for thi
> > if you mean nutrients in the water.  Research has shown that r
> > plants take most of their required nitrogen and phosphorus fro
> > sediment, not the water.
> This is very fascinating indeed. Perhaps all of our supplementat
> should be done within the substrate. It also corroborates the 
> theory that iron-oxide in laterite is useful for fixing phosphat
> in the substrate. It makes me wonder more about the value of a
> slow RUGF system with an iron-oxide, high CEC substrate. Maybe
> it is a case of serendipity that a particular tropical or subtro
> location may support this Aponogeton and one should take soil
> samples and observations there to attempt to duplicate this.

John's comments may be correct as far as they go, but dismiss the 
fact that _many_ of the plants we use in the aquarium are 
(completely or in part) _not_ root feeders, and their needs must 
be met as well. 

Karen Randall
Aquatic Gardeners Assoc.
Boston, MA