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Re: Aquatic Plants Digest V2 #975

> Date: Wed, 24 Sep 1997 22:12:21 -0500
> From: krombhol at teclink_net (Paul Krombholz)
> Subject: Re: Aquatic Plants Digest V2 #974
I asked:

> >...Incidentally, I've noticed filaments extending up from the substrate
> >around some of my Cryptocoryne wendtii that grow in fine gravel or sand.
> >Could these be something like cyprus knees -- a mechanism for the plant to
> >promote the oxygen supply to its roots?

and Paul responded:

> I
> think that these roots may serve to get mineral nutrients from the water.
> They may also function in trapping and holding debris in flowing waters,
> but I have only the vaguest notions how this capability may be helpful to
> the plants.  it may, over the long time, build a raised bed of crypts that
> gets their leaves nearer the surface.  Perhaps the trapped debris is a
> source of nutrients.

I hadn't thought of that.  It makes sense.

Aquatic plants definitely do trap sediments - I've seen this in drainage
ditches and on stream banks where the muck in patches of plants will be
substantially different (darker, probably lighter) then it is nearby in
the channel.  I saw it in one of my unfiltered tanks where 1/2 inch of
low-density sediments accumulated in a thick stand of val.

I imagine there are nutrients in the sediments, but the sediment density
might be too low for it to act as a real soil.  But once it is accumulated
it would host a large bacterial population and multitude of detritivores.
These guys would eventually increase the sediment density and in the
meantime provide through their respiration a source of CO2 for the plants.

I suspect that many aquatic plants are adapted to deal with the
accumulation of sediments in different ways.  For instance, the tendency
of anubias barteri nana to develop exposed roots and to "climb" as it
grows may be an adaptation to keep the plant's young growth above a
steadily accumulating layer of sediment.  I've never seen nana in its
natural setting.  It would be interesting.

Roger Miller