Is Potassium not assimilated by plants ?
 

Elaine T wrote:
Philippe Lemaire (remove oldies) wrote:
Your answer is mostly interseting although some words as cytosolic is not
used every day ;-)

"Cytosolic" means dissolved in the fluid on the inside of a cell. I was
trying to respond to both you and Andrew at the same time.

My main problem is to add Nitrates to keep the level at 30 ppm...
As therfore I add too much Ca or Mg. K comes mainly from TMG and KH2PO4.
If I increase waterchanges, I shall add still more nitrates :-(

Why are you keeping nitrates at 30 ppm? That's part of your problem!
Everything I've read suggests that 5-10 ppm nitates is preferable.
Here's an article on recommended dosing levels.
http://www.sfbaaps.com/articles/barr_02.html I don't even have problems
with nitrates below 5 ppm as long as I'm dosing every couple of days.

My GBA are quite calm since I moved from 15 to 30 ppm nitrates.
Presently, I already put some nitrates everyday not have higher instantaneous values.

Thanks for the help !

Are Ca and Mg cytosolic too ?

Philippe

Is Potassium not assimilated by plants ?
 

Andrew wrote:
Potassium is not integrated into the plant strucure to any great
extent. Potassium is predominantly involved in ion channels. It
regulates potential across the cell membrane, providing energy for
cellular processes, maintaining osmotic pressure, etc. Take away
potassium and the cell's biological processes shut down. FWIW plants
actually have quite a high potassium demand, second only to nitrogen.
Andrew

Define integrated.

By integrated into the plant structure I meant K is not usually
covalently integrated into protein, lipid or carbohydrate structures as
is the case for nutrients such as N and P. It remains in in a free
state in the intracellular matrix.

Remove a plant stalk, and you remove quite a bit of
potassium from the closed tank system. While potassium is mostly
cytosolic and not bound to protein, it is still intracellular (remember,
high Na+ outside, high K+ inside).

Of course, and if you scoop a bucket of water out of your tank you
remove quite a bit of water from a closed system but it doesn't mean
the water is integrated into the structure of the bucket.

That means it is sequestered from the tank water and there is net uptake as
plants grow.

I never said it wasn't sequestered just not iintegrated into the
"structure" of the plant. You do remove a lot of K when you prune, etc.

I believe that is Philippe's essential question, since he is confused about the
accumulating potassium in his aquarium.

Semantics regarding what makes a structurally integrated component of a
plant aside, I believe that question was answered before I posted, ie
yes, K is taken up by the plant so his rising levels of K is unlikely
to be due to the plant not using it, assuming he's not over supplying
it (Given aquatic fertilizers are high in K and Phillipe hasn't said
how much N and P are being supplied by the tank's bioload, this may be
a possibility). Philippe asked a further question regarding what K
does. This is what my post referred to.

As for which nutrients leave a dead plant first, my best guess
(for the reasons stated above) is K, followed by N and P. As a general
rule, it is preferable to remove dead plant matter from an aquarium
rather than leave it to rot.

Plant will often try to retain nutrients where possible. A lot of the
soluble components of dying leaves (eg ions, amino acids, nucleic acids
etc) are transported to the growing areas. What's left in the dead leaf
are usually the structural components which are contain more N and P
than K. When the leaf rots the locked up N and P are released while the
K most likely remains in the living plant.

Andrew

Is Potassium not assimilated by plants ?
 

Andrew wrote:
Andrew wrote:
Potassium is not integrated into the plant strucure to any great
extent. Potassium is predominantly involved in ion channels. It
regulates potential across the cell membrane, providing energy for
cellular processes, maintaining osmotic pressure, etc. Take away
potassium and the cell's biological processes shut down. FWIW plants
actually have quite a high potassium demand, second only to nitrogen.
Andrew

Define integrated.

By integrated into the plant structure I meant K is not usually
covalently integrated into protein, lipid or carbohydrate structures as
is the case for nutrients such as N and P. It remains in in a free
state in the intracellular matrix.

Remove a plant stalk, and you remove quite a bit of
potassium from the closed tank system. While potassium is mostly
cytosolic and not bound to protein, it is still intracellular (remember,
high Na+ outside, high K+ inside).

Of course, and if you scoop a bucket of water out of your tank you
remove quite a bit of water from a closed system but it doesn't mean
the water is integrated into the structure of the bucket.

That means it is sequestered from the tank water and there is net uptake as
plants grow.

I never said it wasn't sequestered just not iintegrated into the
"structure" of the plant. You do remove a lot of K when you prune, etc.

I believe that is Philippe's essential question, since he is confused about the
accumulating potassium in his aquarium.

Semantics regarding what makes a structurally integrated component of a
plant aside, I believe that question was answered before I posted, ie
yes, K is taken up by the plant so his rising levels of K is unlikely
to be due to the plant not using it, assuming he's not over supplying
it (Given aquatic fertilizers are high in K and Phillipe hasn't said
how much N and P are being supplied by the tank's bioload, this may be
a possibility). Philippe asked a further question regarding what K
does. This is what my post referred to.

As for which nutrients leave a dead plant first, my best guess
(for the reasons stated above) is K, followed by N and P. As a general
rule, it is preferable to remove dead plant matter from an aquarium
rather than leave it to rot.

Plant will often try to retain nutrients where possible. A lot of the
soluble components of dying leaves (eg ions, amino acids, nucleic acids
etc) are transported to the growing areas. What's left in the dead leaf
are usually the structural components which are contain more N and P
than K. When the leaf rots the locked up N and P are released while the
K most likely remains in the living plant.

Andrew

Thanks for this precise answer !

So, I know now that pruning remove K but not removing old decaying leaves...
Could you comment also on Ca and Mg ?

I first thought it was related on which type of leaves (new/old) were affected by
deficiencies... However, P, N and K affect old leaves making that not a good critrerion !

Philippe whose English cannot match yours