Re: Allelochemicals, roots and competition

> From: krandall at world_std.com (Karen A Randall)
> > 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 
> competition.

OK, but competition is a good possibility tho? What other 
possibilities are you thinking of?

> > 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. ;-)

No, it would be wrong to suppose that there is a special
symbiosis between these species however Crypts and Aponogetons
do grow in very similar environments and some species do share
the same locales don't they? The oxygenation idea makes sense.
It maybe that the root systems of Crypts don't inhibit this
Aponogeton as much as other plants which live under different
competitive situations. Crypts are not adapted for competing
and (from what I've read) live in less ideal locations where
other plants don't thrive.

> > 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.

And to me this suggests that the plant does not fare well in
a competitive situation. I don't think it's light that is the
limiting factor and it may have something to do with the other
plants which are present or in my situation, it may be that 
the plant doesn't recover well after being moved or disturbed.
Anyone who has had "success" with the lace plant either alone
or in combination with other plants in crowded or uncrowded
situations could please comment further.

I'd like to pick this up again with Charley's next comments
where he makes some interesting points.

> > 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. 

Yes, but John was talking about rooted plants. ;-)

Substrate fertilization might be worth considering as a 
method of limiting nutrients available to algae and some 
of the fast growing water feeders. Also, unlike in nature, 
in a tank we have high concentrations of nutrients in 
the water whereas in nature these tend to be available only
at the roots especially the micro-nutrients. As well,
nutrients in the substrate will also tend to go into the
water solution with time and there should be no shortage of
nitrogen or phosphates since these originate from the food
and fish wastes. It also might be interesting to see how
it would work in a plant only tank!