# [Wet Thumb Forum]-Ammonium vs. Nitrate



## Phil Edwards (Jan 22, 2004)

Is this preferrence somehow related to the stability of the molecules? 

Am I correct in assuming that Ammonium is a less stable substance than Nitrate? 

If so, would this account for the plants' preferrence as it's easier to break down than the more stable Nitrate?

Proverbs 3:7-8


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## Phil Edwards (Jan 22, 2004)

Is this preferrence somehow related to the stability of the molecules? 

Am I correct in assuming that Ammonium is a less stable substance than Nitrate? 

If so, would this account for the plants' preferrence as it's easier to break down than the more stable Nitrate?

Proverbs 3:7-8


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## JaredW (Feb 2, 2003)

Or course the ratio of ammonia/ammonium is dependent on the pH. BTW, plants need to convert nitrate back to ammonium (expending extra energy) to use it for protein synthsis. The following is from Diana Walstad's book:

"Plants, algae, and all phtosynthesizing organisms use the N of ammonium (not nitrate) to produce their proteins...

"The first step in the important GS-GOGAT metabolic pathway is the binding of NH3 to a carbohydrate (GS and GOGAT are acronyms for the enzymes glutamine synthetase and glutamine-oxoglutarate aminotransferase.) GOGAT works with the enzyme glutamine synthetase to bind ammonia to glutamic acid to form glutamine. From this glutamine all other amino acids will be synethsized and then eventually combined to form the plants' proteins."

As to your question, I don't think plants can use ammonia (an anion) directly, but need to take it up from ammonium (a cation).

Plant Resource Page and photos


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## Roger Miller (Jun 19, 2004)

Plants can use either. Euglenoid algae are the only plant-like organisms I know of that can't use nitrate. Nitrate is more energetically costly than ammonium because the nitrate has to be reduced to ammonium before it can be used by the plant. 

It's interesting to contemplate an energy budget for aquarium plants. That is something I've done informally, but really had to approximate a lot of values to get a result. Using my estimates, the difference in energy requirements for growth with ammonium and growth with nitrate could create a 10% difference in the growth rate of the plant.

All in all, that doesn't seem that significant.

I think Tom pointed out once that plants might actually grow best with a 50-50 mix of ammonium and nitrate.

Both ions are charged, so when the plants adsorbs one or the other they have to overcome electrical potential barriers and offset the change in their internal charge balance. That all bears an energy cost for the plant. On the other hand, if the plants can import half of its nitrogen requirement as positively charged ammonium and half as negatively charged nitrate then it doesn't have to deal with the internal charge-balance issue, and the electrical potential barriers may offset.

I don't know if the energy savings from importing a 50-50 mix would offset the cost of getting half the nitrogen supply from nitrate. Things are getting complicated.

Roger Miller


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## Avalon (Mar 7, 2005)

I've wondered this myself. I've come to the (pending) conclusion that it does not matter; however, I'm not considering a situation in which one tank only has NH3/NH4 and another has only NO3--if that is even possible.

I've searched for information on the denitrification process plants go through in order to break the bond of NO3, and from what little information I've found, results infer that there are no significant adverse effects.

I'm still interested in finding out more. Do share if anyone can find anything on this.


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## JaredW (Feb 2, 2003)

"I think Tom pointed out once that plants might actually grow best with a 50-50 mix of ammonium and nitrate."

That's what Flourish Nitrogen claims to be -- N as 50% from nitrate and 50% from complexed ammonium. I'm currently trying it instead of potassium nitrate.

Jared

Plant Resource Page and photos


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## Phil Edwards (Jan 22, 2004)

If plants have to use energy to make NO3 into NH4 then by rights they should grow better when both are present. To me Nitrate seems to be the complex carbohydrate which sustains the metabolism while Ammonium is the sugar which gives it the easy energy. 

If an aquarium was dosed with NH4 _only_ the plants quickly use up the NH4 then shut down, only to start up again with great difficulty. If NH4 consistantly were made available at levels no more than the plants needed then growth should be spectacular. However, I don't see that happening anywhere outside of a laboratory.

With a mixture of NH4 and NO3 the plants have easy energy available to them on occasion. However, when it's gone they still have the NO3 to support themselves with until the NH4 comes along again. That's assuming 100% of the plant mass would use the available NH4 exclusively. 

Having never done tests even close to resembling this I can only guess that in an aquarium where NH4 and NO3 are present at the same time in the right ratios some plants use the available NH4 for quick growth while the rest continue to use NO3 for sustained respiration. Thinking more simply (for my visually oriented brain) the top quarter, being closest to the light, uses NH4 for strong and easy growth. The lower three quarters use NO3 for continued respiration and cell maintenance.

Am I even close? This is starting to make too much sense to me for there not to be holes in my thinking...LOL

Proverbs 3:7-8


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## Roger Miller (Jun 19, 2004)

Phil,

I think you've taken the concept a little farther than anyone could prove or disprove. Maybe your ideas are mostly right, but when you say:


> quote:
> 
> If NH4 consistantly were made available at levels no more than the plants needed then growth should be spectacular. However, I don't see that happening anywhere outside of a laboratory.


I'm not sure I agree.

In a low-tech tank with ammonia provided only by fish waste and without biofiltration the plants are provided with ammonium at a continuous low level. Growth is usually not spectacular in those case. The growth rate is established mostly by light levels and carbon supply. Low-tech tanks are normally (and necessarily) moderately lit with a limited carbon supply.

The difference between ammonium and nitrate as the nitrogen supply just isn't very critical. The nitrogen supply is a secondary factor for growth and whether the nitrogen is supplied by ammonium or nitrate is a fairly minor consideration.

Roger Miller


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## Guest (Feb 7, 2003)

More NH4 vs NO3?

Wish folks would read _all_ of the DW book







She states that the test everyone seems to love to refer to is "either" "or", she had no references to a ratio of _both_ forms and increased growth rates nor gave much info comparing a diverse group of plants etc nor was thing in a CO2 rich environment etc etc etc etc.
She states that also.

She covered the bases pretty good, better than any of the others on aquarium books on most issues. A nice good foot stomping on those past books.

Okay,
That ratio thing: 4:1 NO3 to NH4 is the optimal general *agriculture* crop ratio.
Some plants perfer no NH4, some perfer no NH4.

It's _very_ plant dependent.
Each plant has it's own happy place.
Very difficult to generalize.
I'd like to see some compartive studies on this with perhaps 20 or so species of true aquatics.
But that's not going to happen too soon.

Okay back to transport of N. I know more than I want to know about N and Amino acid biochemistry. Just got done with a doctoral level exam on the subject in plant metabolism. Got _lucky_ and got an A.
Okay some highlights without killing anyone with boredom.
GS(Glutamine synthetase) has a very high affinity for NH4+, about Km of 3-5uM, (very low concentrations).
Now there are two types of GS, GS 1 and GS 2.

GS 2 is found mainly in the leaves at high levels and _only_ inside the chloroplast. GS1 mainly in the roots in high concentrations and is found _only_ in the cytosol of the cell.

There is also primary assimilation ((mainly through GS/GOGAT of N and secondary(recycling of N), unlike animals, plants do not excrete N waste products)) assimilation.

So what's this mean? Well the primary assimilation will take place in the roots namely and the recycling(2nd) will take place in the leaves namely if you look at GS1 only.

So having lots of NO3 in the water column(where the damn leaves are!) and lots of NH4 in the substrate(where the damn roots are!) would be ideal.

GS2 is not going to take in NH4 from outside the cell, only GS1 will do this. GS2 simply cannot get to the NH4 outside the cell, only GS1 can do that. Since leaves do not have much, they are not going to do much NH4 uptake vs the NO3 uptake.

NH4 can be fixed into Glutamine from Glutamate(from the chloroplast) out side the chloroplast in the cytosol and get that NH4 floating around using GS1.

But since there not much GS1 in the leaves, it's not that good at it.

But the leaves are loaded with GS2 which will use NO3 and reduce it to Glutamine and add the N on to the Glutamate inside the chloroplast.

This happens(NO3 reduction in the chloroplast) in the day time a great deal with good reason. There's lots of ATP floating around from the photosystems light reactions so lots of glutamines are produced. Glutamine is metabolically reactive.

In the dark, there's lots of Asparagine. It's relatively inert and is produce preferenially in the dark. It carries more N atoms per carbon than glutamine and there is more an economical compound to transport N when carbon is limitng(plants don't fix carbon at night).

So what's all that mean? Plants are more complicated than folks think. Each plant has it's own preference and niche. NO3 can really be removed much better for aquatic plants since a huge leaf surface area is available.
It'll slop up a little NH4 also, but that's mainly a root thing.
Plants transport some nutrients from one place to the other where they are taken in and processed or made etc.

Exchanging NO3- for H+'s is not an issue since the plant has plenty of H+ and NADPH or 2 Ferrodoxin can also be used from photosynthesis during the day.

Another good thing is that NH4 is typically found in reductive substrate areas, the NO3 in the highly oxidative water column. So these two enzymes are in the right places.

Uptake of N is all the time, but the ratios of certain amnio acids change in the day/night periods.

The issue of energy is important but plants can do very well with either source.
A balance of anion(NO3-) and cation(NH4+) seems to be a good approach from a metabolic standpoint.

At issue is the link between N assimilation and the production of amino acid synthesis.
It takes more than N to make amino acids, it takes a fair amount of carbon and phosphorus to make these and the plant has many ways of balancing out what it needs.

Rather than worrying about something that makes up 1.5 % dry weight of a plant and even less for things like Fe, just make sure _everything_ is available for most of the time.

You will not gain much by swapping one ion for another IMO.

Plants simply do not allocate much to the root biomass increase when there is plenty of N in the water column. I've seen direct evidence of this and research. I'd say it cost MORE to make more/new roots than it does to convert the NO3 into an Amino acid.

So if you have only a bit of root, with all that GS2(NH4), and lots of leaves, with all that GS1(NO3), seems better to give in to the water column dosing methods.

But with non CO2 tanks, the root thing is very good if folks can leave the plants and tank alone.

Some folks always say Crypts and sword prefer root uptake vs water column. I think this is baloney. I have huge crypts and some of the nicer plants I've seen anywhere and I cannot even keep sword plants due to their large tree like stature in my tanks after 6 months. I don't fertilizer the substrate except for flourite and the iron.
If they prefer one over the other, I have to say it's the water column. Why make roots if you don't need them?

Well, maybe that helps, maybe it makes things even worse







I tried to remove most of the funny stuff but I cannot do it without taking out what is essential to the ideas.

Sorry if the biochem stuff freaked anyone out or roast a brain cell or two. I'm sure you'll live.

Regards, 
Tom Barr


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## Roger Miller (Jun 19, 2004)

Great information, Tom.

I guess that among other things this tells me that it makes sense to use an ammonium or urea-based fertilizer in the substrate.

Roger Miller


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## anonapersona (Mar 11, 2004)

Tom, does this explain why some stem plants create so many roots from nodes -- to get at the NH4 that is in the water column?


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## wetmanNY (Feb 1, 2003)

Though photosynthesizers do have these capabilities for getting N from NH4 NH3 or NO3, and though the metabolic pathways are in fact complicated, there is a very simple axiom we are losing sight of, which I believe is true of every living organism, though I can't reproduce its classic statement:

*All organisms preferentially select the least energy-costly locally-available metabolic path. *

This includes protists that switch from oxygen respiration to fermentation, as oxygen levels drop to vanishingly small.

This even embraces organisms' preferential use of the _lighter_ atomic isotope, in using N or O to build structure. Paleobiologists use this axiom to determine the amount of ice pack that existed when a fossil shell was laid down, by the minute differences in certain isotopes.

In photosynthesizers, NH4 is used preferentially to NH3, as less expensive, and the machinery for metabolizing NO3 isn't switched on until ammonia/ammonium gradients are vanishingly low.

As another example: as long as there's some nitrogen available as NH3/NH4, nitrogen fixation in cyanobacteria won't switch on. Unnecessarily expensive.

Remember too that NH3/NH4 is not just produced by the fish. It's part of every cellular respiration and it's also produced in decomposition of organic matter. There are many sources of ammonia in an aquarium ecosystem.


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## wetmanNY (Feb 1, 2003)

Sorry I cut myself short:

To return to Phil Edwards's initial question: the documented preference of algae and plants (euglenoids are best left out of "algae" metabolisms) for ammonium over nitrate isn't related to the comparative stability of one of these N-bearing molecules vis-a-vis another, but rather to the ease with which the N can be metabolized. N has to be converted first to NH4 before the complicated reactions Tom Barr has recently aced on his exam can get started.

JaredW and St. Diana were onto the right track. Wasn't JaredW right when he posted: "I don't think plants can use ammonia (an anion) directly, but need to take it up from ammonium (a cation)." And of course Roger Miller was also right when he answered that "plants _can_ use either."Nitrate is more energetically costly than ammonium because the nitrate has to be reduced to ammonium before it can be used by the plant," he added. An extra energy-using step.


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## Guest (Feb 7, 2003)

But the idea you are saying is simply, too simple.
Plants need both generally, not one or the other to function best.
This has been proven many times.
Some enyzmes are better at one job than another even if strikingly similar like isoenzymes like GS1 and GS2.
Some enzymes are in the wrong(or right place depending on how you look at it) place.

Plants have adapted to deal with many situations, not just the ideal.

NH4 toxicity really becomes a huge issue if you attempt to add enough to staisfy the Nitrogen demand for most plants. NO3 is far less toxic and this concept extends over to fish health and welfare as well.

Algae have GS1 etc as well. The enzymes in algae possess extremely high affinities for NH4+, much more so than NO3.

But the deal is not so much an energy issue as it is a simple issue of having ANY source of Nitrogen available to make amino acids.
Things change in the environment and your tanks for that matter.

Aerial Roots are forms for reasons not yet clear. Cannot say much there. They(Aerial roots) don't possess root hairs though.

You can add NH4 to the substrate but it's naturally reductive anyway deeper down. 
So adding more N might cause big problems if you pull it up and folks that prune etc often will invariably do this.

The only way to really add NH4 and not be burnt is with fish and critter loads. I've used ammonium sulfate etc but I don't think folks should play unless they have other motives besides a nice plant tank.

Adding NH4 is a bad idea and simply not needed nor will it make any tank significantly better.
I'd not fret or worry about it.
Regards, 
Tom Barr


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## JaredW (Feb 2, 2003)

Diana says in her book that ammonia is simply too risky to add directly if you have fish. I was under the impression that ammonium isn't toxic, but you would have to ensure it stays as such -- as Seachem evidently has done. You might be able to combine ammonia and Amquel, but that might get expensive.

Jared

Plant Resource Page and photos


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## Phil Edwards (Jan 22, 2004)

Tom,
Yep you fried a few brains cells with that big one. I've got yet another question. When water is brought into the substrate, either by root action or undergravel heaters, is the Nitrogen then reduced to Ammonia, vice versa,not at all, or what?

If plants utilize NO3 more effectively through leaves why is it that swords and crypts continue to grow such large root systems? Is there really *that* much NH4 in the substrate or do we go back to the above question?

Roger,
Unfortunately the only tank I've ever had with no N addition was a long time ago and had Java Fern and Moss only. I've recently set up a tank with H. corymbosa (angustifolia), a couple odd crypts, and Phylantus fluitans with an RUGF for filtration/current and DIY CO2. I'll dose P K and traces as normal for a low light aquarium (set amounts to be posted once I determine the amounts needed) I'll refrain from adding N to the tank outside of fish and food and We'll have ourselves a little experiment.

The fish load consists of 6 Cherry Barbs and 3 Spiketail Paradise Fish.

Thanks to all of you for your input, I'm getting a much better understanding of all this now. Perhaps one day I'll be able to ace _with luck_ a 100 level botany test..









Proverbs 3:7-8


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## Guest (Feb 8, 2003)

I might be wrong but I believe that only the green things will go from NO3=> NH4. Once NO3 is present, it can either hang out, get assimilated by plants/algae or get turned into N2 by anaerobic bacteria.

Fish waste settles down into the substrate and can build up over a year or two.

Crypts and swords live in variable environments. Some times of the year they are underwater along side of a river. Roots help them to hang on. When rains come and wash off all the Nitrogen into the river they take in the NO3 from the water column.
When later on they waters recede, the plants are exposed to ther air.
No usable nitrogen in the air. So they use the roots to get the NH4. 
More root growth is allocated when the plants are emergent. They have more CO2, light etc.
Most swords and crypts come from places like this. They are more emergent plants than true aquatics.
There's not much NH4 in the substrate to begin with even in richer tanks.

You folks can go on and on about NH4 vs NO3 but the fact of the matter is that it doesn't improve growth significantly in every practical tank set up I've ever done. 
I simply don't see a 20% improvement in growth rates or even 5-10%.

Why bother. If you like biochem, then it's great.

I'll try and get this through again here.
The issue of energy is LESS important than the issue of having nitrogen itself. There's plenty of light for energy.

Having nitrogen is the main goal here for most plants. They have plenty of ATP and NADPH from the photosystems.

If the plant becomes nitrogen limited they are much worse off than ANY issue to due with having to use some extra energy (and not that much), they simply cannot make the amnio acids and not much can happen then.

In nature, plants adapt to N limitation conditions.

It takes a great amount of energy to make the enzymes and put them where they will do the most good for N assimilation.

Needing to make fewer enyzmes in itself can be a susbstantial energy savings. The plant has choices, make this enzyme or that enzyme to get the needed raw materials to make tissues.

There's a nother set of of the these enzymes involving the NADP GOGAT(Roots) and Fdx GOGAT(Leaves) in a similar issue like the GS1 and GS1.
I left that out to keep it simple.
It involves photorespiration and recycling of the NH4 from the Chloroplast<->peroxisome <->mitochondria back into the assimilation.

Then there's another enzyme, GDH may use ammonium when it's plentiful for assimilation. Generally it plays a catabolic role.

These enzymes are linked together with feedback systems.

You can go very deep into the why of theory but the proof has always been in the pudding.

I've tried it in plant tanks, I see no significant gain and perhaps a nasty algae bloom. 
So while interesting in some respects, I don't find the info particularly useful in application.

Use NO3 and quite worrying over nothing which it really amounts to in our case.

Regards, 
Tom Barr


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## Avalon (Mar 7, 2005)

"Use NO3 and quite worrying over nothing which it really amounts to in our case."

KNO3!
True, I completely agree with Tom here.

On another note, which may be off the subject and grounds for another thread, but Tom, I think you underestimate the role that roots play. Granted the roots of stem plants really don't matter much, as many tend to trim them off every week or two, but I do think that roots play a considerable difference. I ran across a study that gave them considerable credit. I don't think now would be the best time to get into this (cold beer time







), but I would like to discuss this with you if you and get your ideas and opinions.

My D.W. book is on it's way (I can't wait!), and for the info guys, the Cristel Kasselmann book, Aquarium Plants, is available at Wal-Mat online for $44.89! It's the hardcover and carries the same ISBN# as the one on Amazon.com! Unfortunately, it's currently out-of-stock. I hope they get more in! I thought I'd give you guys the heads up! Checking back is worth the $40 savings!

http://www.walmart.com/catalog/search-ng.gsp?cat=18865&search_query=Kasselmann&CATEGORY_ID=18865&dept=3920


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## JaredW (Feb 2, 2003)

I hope they honor that price, since they have it as 10% off a list price of $55.01, when the actual list is $84.50.

Jared

Plant Resource Page and photos


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## Guest (Feb 12, 2003)

I have a German version auctioning at ebay. I think it's at 5$
It's great for pic's which is what most books seem to end up as.

Regards, 
Tom Barr


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