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Re: taking a breath

Roger S. Miller wrote:

> Ole Larsen quoted Ole Pedersen regarding the
> interplay of growth limitation by light and CO2.
> Mr. Pedersen questioned outright the value of Liebig's
> rule of minimum's.  We use Liebig's rule to justify algae
> control methods, build fertilizer regimes and found
> entire aquarium care philosophies, yet his statement
> fell without discussion.  Noone has anything to say?

( once again for emphasis )
> Mr. Pedersen questioned outright the value of Liebig's rule
> of minimum's ....

I did catch that post.  It disturbed me.  I think in Liebig's day and
today everyone can agree that higher order plants can generally store
nutrients and have the ability to "mobilise" many of the stored nutrients
where needed. (where deficiencys exist)  In todays world it frustrates
me that there is a dearth of knowledge regards nutrient uptake /
of  aquatic plants.  Yes, there is limited analysis using radioactive
which is common-place in other areas of science but how I wish there
was more with aquatic plants.  My point is I have felt that Leibig's law
is clouded by a plants ability to store nutrients,  our inability to really
know how those nutrients are mobilised,  and therefore, when is a nutrient
truly "the limiting" nutrient.

In support of my feeling that we don't understand enough about nutrient
movement, I would like to share the following recent observation. I have
magnesium levels in the water column that have increased after my past three
water changes even though the (tap) replacement water has lower levels of
magnesium than the water column.  The only source of magnesium I have
is the result of MgSo4 supplementation about a month ago.  I am convinced
that the increase in Mg in my water column following the past three water
changes is comming from the plants.  This  suggests ( in the face of
on the APD I have to confirm it ) that the movement of the Mg ion is
bi-directional.  I also suspect that there is some relationship between the
movement of "important" ions  ( Ca, Mg, K ) inside and outside the plants
which hasn't been discussed.  Toward that end, I have purchased a LaMotte K+
test which will supplement Mg+, and Ca+ tests I  have and will be used to
monitor Ca, Mg, and K ion levels in the weeks and months ahead.

Here is some of my very preliminary thoughts. It is fairly accepted
that potassium plays a role in osmotic balance.  With the K+ test, I
am  hoping to quantify the deltas in the water column of K, and hopefully
find some meaningful correlation between the three ions of Ca, Mg, and
K and to establish that these ions move into AND OUT OF the plant.
Assuming this can in fact be quantified, I also hope to speculate:
1) Ions IN MASS (i.e., not selectively), are moved inside and outside
    the plant in response to an  'osmotic'  pressure gradient inside and
    the plant of  either total ions
2) that the nutrient uptake in aquatic plants is more osmotic in nature than
    we have preveously given credit.  This would lend support to my belief
    that you can have a deficiency of an ion within a plant even when
    levels of that  ion exist in the water column.
3) that the roots of aquatic plants play a more important role in uptake of
    Mg, and K ions than has been mentioned.

Now mind you,  I am no scientist.  But I do seek the truth here.  And I
there is room for exploration.   Since I think I'm headed to unchartered
waters here
with all this ion monitoring,  I'd appreciate the feedback of any other
aquatic plant
nutrient enthusiasts, enquiring minds, etc.

Christopher Coleman
christopher.coleman at worldnet_att.net