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With what replace KNO3 ?

_Maq_ said:
Not sure whether I've understood the context but plants cannot convert ammonium into nitrate.
In general, I've studied more than just a few papers on the question of nitrate vs. ammonium nutrition of plants, esp. submerged plants. In sum, it is believed that aquatic plants slightly prefer ammonium, yet in most instances, plants grew best when both ammonium and nitrates were available.
The issue is not that simple just to say 'assimilating ammonium is less demanding energetically'. There are circumstances which must be included into account.
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Share them. I’m keen.

The obvious caveat to every single post ever written by every single hobbyist is that things cannot be generalized to every species.

Certainly, the natural environment will dictate the mechanisms present in a plant.

I don’t dispute that there exists an optimal ratio given a particular species. However, it wouldn’t make much evolutionary sense if the mechanism did not exists: it could be less efficient and cost more energy or even be unable to keep up with any demand unless metabolic rates were increased.

I would be rather interested - leveraging Leidbig’s - if we could compensate any of the observations by supplementing higher co2 levels and/or all nutrients associated with the mechanisms —- I say co2 as undoubtedly, it has the highest probability of making a difference.

No matter how you slice it, if you don’t provide the exact amount for a fixed moment of time, there is an associated cost (and that will be energy) — glucose, co2, etc.

Josh
 
JoshP12 said:
The obvious caveat to every single post ever written by every single hobbyist is that things cannot be generalized to every species.
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In fact, plants differ by outer appearance much much more than by their physiology. Proteins and enzymes are largely the same in all higher plants. The reactions they execute are the same, and so are the energetic budgets.
JoshP12 said:
I don’t dispute that there exists an optimal ratio given a particular species.
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There's much more to that. External conditions existing in every moment can influence the energetic balance of many processes. Par example, while uptaking nitrate, a proton is co-transported. That is energetically 'cheaper' in acidic environment - full of protons. On the other side, when ammonium is taken up, a proton is exported. That is easier in basic environment. Similarly, the presence and intensity of light, the presence and concentration of certain other ions, even the concentration of CO2 influence the plant's choice at every moment. (That's why Diana Walstad's statements on this issue are primitive and scientifically incorrect.)
 
_Maq_ said:
In fact, plants differ by outer appearance much much more than by their physiology. Proteins and enzymes are largely the same in all higher plants. The reactions they execute are the same, and so are the energetic budgets.
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These are very detail-oriented statements.

Two bodies also have the same insides … yet they function completely different under different conditions.

Energetic budgets for the specific mechanisms may be unique, but it is not so simple. You require certain constituents, you have reaction rates, you have concentration gradients affecting the efficacy and yields of these reactions.

There's much more to that. External conditions existing in every moment can influence the energetic balance of many processes. Par example, while uptaking nitrate, a proton is co-transported. That is energetically 'cheaper' in acidic environment - full of protons. On the other side, when ammonium is taken up, a proton is exported. That is easier in basic environment. Similarly, the presence and intensity of light, the presence and concentration of certain other ions, even the concentration of CO2 influence the plant's choice at every moment. (That's why Diana Walstad's statements on this issue are primitive and scientifically incorrect.)

I suppose we should add the other caveat to every post ever written - it depends on the environment and is unique to all that stuff.

This is an interconnected web and dynamic system —

Thanks for your marchner post ps. Won’t take it at face value — not sure it makes an evolutionary sense to negate the ability entirely … the efficacy of the mechanism sure … but a system has access to different forms of N even if you just “dose” NO3 … decay … substrate … fish … etc.
 
JoshP12 said:
Won’t take it at face value — not sure it makes an evolutionary sense to negate the ability entirely
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The enzyme which would enable such reaction is known to exist in bacteria but not in higher plants.
Maybe it would come as a surprise to you, but there are many seemingly good things that higher plants cannot do.
 
Y'all, I don't always agree with @_Maq_ , but the fact that plants uptake nitrate and then have to reduce it to ammonium to use it, not the other way around is super basic plant science and highly conserved across plant lineages. There are so many things that vary by species, including which nitrogen source is preferred, but this a very fundamental building block of how plants work.
 
Hi all,
ElleDee said:
but the fact that plants uptake nitrate and then have to reduce it to ammonium to use it, not the other way around is super basic plant science and highly conserved across plant lineages.
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<"That one">.

I really <"enjoy these threads">, and I think the research done by @_Maq_ , @Geoffrey Rea & @Roland is invaluable, but personally I'm really not too bothered about which <"form of fixed nitrogen"> we give our plants. I can't imagine any of us are ever going to <"add enough TAN"> to cause plant issues. Additionally, with certain provisos, we can estimate the amount of stored nitrate (<"luxury uptake">) by <"plant colour">.

I've got a method that works for me, just ensure your <"dissolved oxygen supply"> always exceeds your (potential) <"Biochemical Oxygen Demand (BOD)">. I just think plants (including some with the <"aerial advantage">) are the <"easiest way of doing this">.

It isn't <"very exciting">, but <"it works"> and is <"accessible to every-one">. I want people to keep <"successful planted tanks">, because planted tanks make the <"rest of aquarium keeping so much easier"> and more enjoyable.

cheers Darrel
 
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