[APD] RE: N

["Thomas Barr" <tcbiii at earthlink_net>]

> How much N can be stored by an aquatic plant beyond its immediate needs?

Oooooo, depends on the individual plant species and the nutrient status of
the plant and also the size of the plant(eg some plants with many leaves
that act as storgae organs will fair much better).
There's a dozen of other issues but these are just some.
 
> Can a macrophyte increase the levels of N in all the tissue or only in the
> growing parts?

All tissues.

> What is the mechanism of N absorption?

Err what forms? NO3, nitrate reductase.
The affinities vary from plant to plant very often.
The amount of NH4 present etc.

> What are the chemical intermediates of N metabolism?

You'll need to be more specific, pathway leading to what?
Glutamine? NH4+?  

> How is N used within a plant? by that I mean in what chemical forms &
> morphological parts of the plant?

Pretty much most all parts in the cellular levels.
Cell wall, cytoplasm, organelles, DNA, Ribosomes, Endoplasmic reticulum etc
etc.

> Is there any difference between N consumption & use for filamentous algae
&
> rooted macrophytes?

N/P ratios for FW algae is about 14:1
N/P ratios for aquatic macrophytes: 10:1

As far as consumption, well goes back to part A above.
Algae are better at needing less N, have high affinity at low
concentrations of N.
Plants have more storage and organs that can access N sources, less surface
to volume ratios.
Plants will have a faster uptake rate at higher N concentrations(NO3 or
NH4+, PO4 etc) 

> Steve P
>
> PS Hint: many of these questions can be answered by someone with spare
time
> using a search engine like Google. For some, we probably need access to
> botanical research material.

I've talked about N metabolism in the past here Steve.
I discussed Glutamine Synthase(GS1 and GS2)/GOGAT etc etc.

I think it fried a few folks.
It's not simple and I distilled what I knew.

Regardsm, 
Tom Barr



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