I re-read that whole page a bit more carefully. I would like to see more studies done on how fast submerged plants take up ammonia vs. nitrate. Water lettuce and duckweed are both floating plants, elodea is the only submerged plant they have data on there, in the graph. Floating plants are a bit different than submerged plants, one major reason being that they are not co2 limited since they are getting their co2 from the air. So they grow much faster and probably therefore behave a bit differently from a submerged plant, so it's a bit of a stretch in my mind to generalize this data to other submerged aquatic plants living in a low co2 environment.

It's also very likely that this experiment was done under high lighting (water lettuce needs high lighting) so nitrogen uptake was basically being driven as fast as possible. That also may not be a realistic set of circumstances for our purposes. Lighting can also have a huge effect - slnce light drives growth, and therefore uptake too. A plant under very high lighting may react differently to ammonia and nitrate than a plant under low lighting, where their nitrogen needs have slowed down considerably. CO2 injection may also affect how a plant deals with ammonia and nitrate, since that plant would be far less carbon limited, and in fact need to use nitrogen much faster. The hypothesis is put forth that plants prefer ammonia because it takes more energy to use nitrate. However, if that were all there was to it, you should see the ammonia level on the Elodea graph go right down to 0, before nitrates started being used. Why use nitrates at all, when ammonia was still available? There's still something unanswered there, at least in that data.

There's also the question of adaptation. Plants do adapt to their environment, and if they are transplanted to another environment, although just as suitable, they may stop growing for some time and go into a state of inactivity as they adapt to their new circumstances. What we need to know, is how fast a plant that is adapted to a very low ammonia, moderate nitrate environment can take in nitrogen, as opposed to another plant adapted to an environment with solely ammonia as nitrogen.



Floating plants are usually recommended for el natural tanks, and this is sensible considering the fact that they can take in ammonia at very high rates as is shown.

Hi Helen,

Yes, Plant Physiology, (Taiz Zeiger, 2nd edition, 1998. I'm sure they have 3rd and perhaps 4th out by now). Ref: figure 12.6, page 328 T&Z 1998.
The citation that Taiz refers to comes from Pate , 1973.
BTW, there are no less than 4 pathways for NH4 assimilation in angiosperms and some are reversible(eg GDH pathways).

Some pathways, such as AS, are inhibited under high light and high CO2..........
and are low in C, whereas the plants will produce the typical GS/GOGAt pathway Glutamine if they have ample Carbon available. Thus this links amino acids Glutamine and Asparagine to N and C metabolism.

Both of which can change a lot in aquatic systems.

So.....what might occur when you add high levels of enriched CO2 gas to water?
High vs low light? You can see it's not nearly as simple as we might think initially.


I have given it thought for several years.
I think about applied issues.

Under so called aquarium field conditions, we do not have equal fractions of N-NO3 and N-NH4.

We have far less NH4 and much more NO3.
In sediments, we likely will have far more NH4 and much less NO3.
Plenty of evidence to support this observation over decades from virtually any aquarists that bother's to measure NH4.

Do you think adding 2ppm, or 0.5ppm of NH4 etc is a good piece of advice?
Why do aquarists even need to bother buying KNO3, KH2PO4 etc when we can just add terrestrial based fertilizers?

I've taken out the sediment issue and have added it back over the years. I've done long term non CO2 planted tanks with KNO3 dosing and inert sediments as well. Most seem to suggest it works better. I contend and mixture of sediment based and water column based nutrient sources is best.

That is to say, they are synergistic.
The same applies to NH4/NO3.

I think overall though, the bottom line is that as long as the plants have some source of N that's somewhat stable, you really are not going to see much difference in growth.

If you vary CO2 on the other hand, you will see dramatic differences.

[quote]
I agree that a study of one species doesn't necessarily apply to all species, and I haven't checked the original references for the following figure in Walstad's book, which list 29 plants that prefer ammonia and 4 that prefer nitrate.
[quote]

I'm only interested in submersed species as they are the ones of interest to most aquarist. There's only (5-7) ref's that address that, whereas all the submersed NO3 preferences are submersed(4). There's no bacterial NO3 production in peat bogs or other similar aquatic systems anyway, so they have little NO3 available anyway.

There is a lack of information, we cannot make such over arching comparative conclusions based on what we do not know..........

We have some 300+ species, and data for 10 or so there in her book.
Of those, most are weedy highly aggressive cosmopolitan species which can grow well either way(NO3/NH4).

Schuurkes et al, 1986 for the NO3 comparisons.


Is NO3 uptake transport enzyme inducible or constitutive?
General, they are inducible and have various concentrational inducement for several groups of NR enzymes.
NH4? => HATS constitutive

Reddy et al 1987 looked at NO3 and NH4 in various species including Egeria. At higher levels of NH4, this same relationship held true. However, Reddy noted that much of the NH4 was taken in and converted to NO3 for storage.............

And unlike this study, they used 12 ppm of NH4 and had a lower range values at 0.5ppm, well in the range of test methods. Actually, DW cited this paper as well.........I know Reddy personally, and had a grad class with him on aquatic sediments.

The rates look at the same if not higher for NO3.
This is also about the time that it takes to induce Nitrate reductase in many plants once exposed to NO3.

And given the inducible nature of NO3 uptake..........and question for you is how where these plant acclimated prior to this test?

They where not(well, 3 days........come on, that's not much and at 30 micromols of PAR) They used them from NH4 rich sediments and washed etc, then added.
They used 3 replicates..........not much...........
They noted that old shoots died............and new ones formed...........

This suggests that the plants where not acclimated to the conditions adequately........

I can also tell you without any reservations, that these two plants do extremely well at 5ppm of N-NO3(22ppm or so NO3). See Gerloff 1966 for more.

They where poorly adapted. I would not try to say anything horticultural about them, perhaps a pulse of 2 ppm of NO3 and NH4, but not a continuous flow of 2 ppm from a source.

What would happen if they added another pulse of 2 ppm of each form of N at say 16 hours?
96 hours?

Or maintained the 2ppm over 64 hours?

Are Relative growth rates different between treatments?
If so, how much between the NH4 vs NO3?

Looking at the bar graphs(Fig 1), the significance test between NH4 vs NO3 and NH4+NO3 are not statistically different using Mann Whitney U test. Fair amount of variation in the data and low replicates.........

I'm not so sure........

Over 14 days, the levels of change in NH4 and NO3 with 2 ppm were the same.............

Perhaps.
Still, not many folks have aquariums where they have such ratios, typically they are even higher, in the 1:50 range or more and rarely is NH4 ever more than 0.1ppm.


Yes, perhaps true. They do not tell us what method they used, however, Standard Methods suggest there are several methods that are pretty accurate.

Or perhaps they do and the plant has already taken up enough NH4 and starts switching to NO3 as a storage once the NR is induced.

Hard to say over this short time frame and with static starting points at high and equal concentrations. Something rarely seen in aquariums.

My instrument sitting here is accurate to 0.017ppm using Nessler's.

https://www.hach.com/fmmimghach?/COD...NE_OTH2069%7C1

But only 0.09, about what they have using the Salicylate.........
Seems I'd want to know more there.
Also, there's no error bars on those 3 reps for the test on Figure 5, the one used for support .




NH3 measurement has been around for many years.
Standard Methods for the Examination of Water and Wastewater suggest 0.03ppm.

http://www.umass.edu/tei/mwwp/acrobat/sm4500NHprobe.PDF

Phenate is good from 2.0 to 0.02ppm.

ScienceDirect - Sensors and Actuators B: Chemical : Amperometric determination of ammonium with bienzyme/poly(carbamoyl) sulfonate hydrogel-based biosensor

2.06 uM seems pretty low to me.

No clue when or if they had less accuracy when the study was done or even what method they used. I'd be plenty careful if I where them however and find a really good test method for that given the importance of it and the relatively short time frame.

I think Nessler has been the standard for nearly 100 years and should provide very low ranges. It's not used much these days. So they may have had some acclimation issues and testing issues, we can only speculate.

Artificial relative to what?
Plants still remove Nitrogen.
Bacteria are a natural part of the aquatic system.
Whether it's from NH4 or NO3, it really does not play a large role as suggested in the Ecology of the Planted Aquarium.

The Relative growth rate data supports that over a 14 day time frame.
The authors in the study concluded that these two plants prefer NH4 over NO3, however, they said so based on them being the same concentration.

I prefer to have more filter as a back up in case plant growth wanes for a variety of possible reasons, and have a redundant back up.

The gain is not worth the trade off.
I'm not getting much out of this deal.

Good current is more worthwhile
Ability to add carbon, any media etc
Handle higher bioloads.
Reduced NH4 toxicity.
Better response to shock loads

I'll keep my filter.
I've shown for many years that we can induce algae blooms using NH4(you cannot do it with NO3 however) and that a good bacterial colony reduces the potential for an algae bloom.

That + toxic suggesting 200-13000X more toxicity for NH4 vs NO3, I do not think the trade off is worth it.

Still, the general approach you conclude is similar to my own, have a back up for both the filter and the plants. I’d be careful not to be swayed to those that suggest planted tanks should have no filters and that you get this large gain out of that approach. I’ve seen more algae blooms and less resiliency in such systems and dosing NH4 also tells you a lot of the potential issues that can and do arise. I think the Neophyte seems initially enamored with filterless planted tanks, till something goes wrong and there’s no filter for a back up.

Thanks, I found some new info along the way as well.
I wish I could say more about it, but there really is not the specific answers available we need to speculate more.

However, we can add various sources of N as NH4 and NO3 to non fish planted tanks and see, as well as various locations.

I'd say the source and type in the sediment plays a larger role than the water column for NH4. And NO3 plays a larger role in the water column overall.
We cannot have high levels of NH4 in the water or the sediment interface, however we can have NH4 embedded in sediment, clays etc.
NO3 is relatively non toxic and a good storage form of N.

This way we cover all the bases and do not get stuck in the "either or" dictomy.
The reality is that nothing is that black and white.


Regards,
Tom Barr

Thanks Tom,

You raise some really interesting ideas, and make it clear how much there is for me to learn about this (not that I supposed otherwise - as a physicist I am well aware of just how much detailed knowledge goes into any scientific field).

I'll start with Taiz Zaiger: Plant Physiology, assuming my university library has it. When I get a chance (heavy workload, heavy life-load at present).

One question you asked: the researchers in the paper referred to by Walstad (Ozimek etc) say the following about their method:
" PO,-P was determined according to Murphy & Riley (1962), NO,-N according to Stainton et al. (1974), and NH,-N following Verdouv et al. (1977), using a Cerco automated analyzer."

The Verdouv reference is the following:
Verdouv, H. C., J. A. Echteld & E. M. J. Dekkers, 1977. Ammonia determination based on indophenol formation with sodium salicylate. Wat. Res. 12: 399-402.

I suspect it might be familiar to you I read it, but could find no clear statement on the lower limits of accuracy for the process. There is a calibration curve in the paper, but it wasn't clear to me whether that should really have been drawn down to zero or not. So I was still confused on that point, and started googling randomly to try to figure out the accuracy of measuring ammonium in general. As you so gently pointed out, I didn't get very far with my googling

In my opinion and experience (which is much more extensive, have to admit, with terrestial plants than aquatic plants), plants naturally will grow and you have to work at stopping them more than you have to work at starting them growing. They have evolved to grow and that is one of the things they do best. So they can be trusted to do their stuff. Yay for plants!

Thank you for the discussion.

Helen

In general Salicyate methods are worse at lower detection limits.
So that level of detection seems plausible at 0.1ppm.
Still, I'd want more as a researcher when doing this set up.

The Bioenzyme method is neat, but not practical.
Nessler's is phased out due to Hg issues.
So phenate seems pretty good.

I have a Hach DR 2800 and phenate here at home.
This can target pretty low NH4, but still not as a good as enrichment with N15 and it's smaller than a Cyclotron

A question that's dogged me is "who" gets what for each NH4 added to the system. How much goes to bacteria, periphyton and algae spores, adult algae and plants.

I could test many plant species within a community or ecosystem all at once and discriminate.

Reddy had a nice meter cube wetland soil sediment flooded system at his lab that was suited well for this. Adding enriched NH4 and NO3 would be ideal, but taking over it for a few months would be tough, but I was studying algae at the time
The mass spect was pretty good but they had it set for natural backgound levels, not enrichment studies so I was sort of talked out of it by the lab guys. Bastards

I could have used another spect, but they are squirrley.

I think the bottom line is much more basal. A simple test, something aquarist can and do. By already adding NH4 only, then trying NO3 only, then using both at once at say low NH4 and higher NO3, you can see if you can note a growth difference or not.

While accurate dry weight measures are good and certainly wise in research etc, for most aquarist, if they cannot see a difference visually in rates of growth they can definitively say is due to the treatment, they really will never be convinced.

I'm very much Socratic in this respect, I'd rather folks try it themselves, see what they think and can conclude. They need to ask the questions, then go about setting up a test to determine if the hypothesis may or may not hold true, or, if it remains inconclusive.

Simply thinking about what we can do, rather than what we cannot, and all the labor and resources involved, can answer most of the questions aquatic plant hobbyists may have.

Then the person convinces themselves, not merely taking my word for it.
I hate that when they do that. Then they can argue for it (or against it). If you have not done it, then you cannot talk much based on experience and observational data and test will only get you so far. Manipulative test can be done here fairly easily and are much more powerful.

But......Many do not want to induce algae, risk fish losses, to answer a question about what might cause algae blooms or if there's really that large of difference between N sources. I do, and I can get rid of algae and start anew easily. Most cannot. They get a tank stable and the last thing they wanna do is mess with it.

Diana's notions about Allelopathy have been falsified easily with respect to algae control. All it takes is a very simple test as a control, often used in terrestrial systems, add activated carbon to the filter at high flows and lots of Carbon vs tank volume.

Ho: algae will bloom
Ha: algae will not bloom

Algae did not bloom in non CO2 nor a CO2 enriched tanks.
Same type of thing with adding PO4, NO3, Fe etc to excess levels in both types of aquariums(CO2 or not, side note: Excel kills algae and bacteria directly, so it's not the best carbon source to consider).

I did not need to do a large scale study to figure out most of the relationships in plant, algae and fish interactions and interdependencies.

What was not considered nearly as much was why plant- plant allelopathic issues where not considered with the same zeal. These are common in terrestrial systems and AC is the control for those systems as well.

If it's dramatically significant enough to see it after a few months, then the results tend to be fairly strong. More subtle relationships are harder to differentiate, but fewer folks will see the same things also. Why put effort into something that does not yield good returns for the effort and the risk? More than Plant Biology, a lot of it is human sociology/behavior and common sense logic.

Adding CO2 gas vs not is a dramatic increase.
Adding PO4 to a limited tank is dramatic.
Adding N to an N limited tank is a dramatic increase, same for adding K+ and Mg.

Traces are more subtle, but still there.
Light is huge, the largest factor.
CO2 next and then on down the line for the nutrients.
Light drives the CO2 uptake which drives N which drives K+, PO4 and so on down the line.

Adding fish to the tank adds a fair amount of continuous low level NH4, ideal for fish tolerances and preventing algae and adding a source of cationic N.
I've never noted that much difference in health or growth however in Fish or non fish planted tanks after many years. Still, that is the typical case for most aquarist: fish + KNO3 dosing or a sediment nutrient source + fish.

FYI, plants can and do take up various amnio acids as well, then the N sources are no longer toxic and already usable. Eg Glycine.........

I detailed out a Nitrogen article here in the BarrReport about 3 years ago now, I addressed the adaptation issue with NO3 and various transporters in plants.
Also, the strong covariance between CO2 and Nitrogen in submersed aquatic plant growth and health.

Overall, most folks in the field know aquatic plants are opportunistic, they will take whatever form is around and wherever is might be(sediment of the water column, internally, organic vs inorganic) and grow like a weed.
They really do not seem to be that picky.



Regards,
Tom Barr

Thanks again for the discussion. Sorry I've been slow to respond - I got caught up in family affairs, had to attend a funeral, and am now back catching up with everything.



Could you please explain this in more detail. I'm not familiar with your Ho: and Ha: terminology. But I'm guessing you said that with the carbon in the tank the algae didn't bloom and that without it the algae did bloom.

What I don't understand is what conclusions you could draw from that, other than that carbon helps to control algae. As I understand it, carbon absorbs (adsorbs?) a lot of stuff from the water, presumably including some of the allelopathic compounds. It also doesn't absorb (adsorb?) some stuff from the water. For example I have read that it is bad at removing copper. So presumably it doesn't remove some of the different allelopathic compounds. How can you know exactly what the carbon is doing, and, given that it's changing the water chemistry significantly, how can you draw specific conclusions about allelopathy and algae from that?

It seems to me that aquarium systems are so complex, even when kept intentionally simple, that it is going to be impossible to untangle one set of cause and effect (for example: one allelopathic compound produced by a plant and its effect on algae in that aquarium) from all the other things with which they are entangled. In this situation, isn't the only way to study things to do so in isolation from the aquarium environment. By, for example. isolating the allelopathic chemical in question and testing the growth of bacteria or algae in its presence?

As I understand it from Walstad's book, this has been done, a little, and the experiments show clearly that the compounds from the plants do inhibit various kinds of bacteria, algae and other plants. Which makes perfect sense to me, as terrestial plants are certainly sometimes poisonous to some kinds of other forms of life, including humans.

The next most simple experiment that could be done would be to grow a single kind of plant in a very simple system, maybe just a glass of water, and see whether algae is inhibited by the plant compared with similar systems without plants or with different plants. If I remember rightly (don't have the book here to refer to), this has also been done, though not extensively, and the results also supported the idea that some plants inhibit some kinds of algae and that allelopathy may be the reason why, or one of the reasons why.

I guess it just doesn't make sense to me, given that many terrestial plants use poison extensively to compete with other organisms, that at least some aquatic plants wouldn't do the same thing. Maybe I am missing some key difference between aquatic and terrestial plants here.

In any case it's interesting!

No problem at all.........we all cannot expect to do this 24/7


Not quite. In both cases, algae did not bloom.
In a healthy tank without algae of AC: no bloom.
That is the observation that most folks see in this hobby.
the test or treatment in this case is to take an otherwise healthy aquarium(you need a good reference point) and add AC to the filter. Since algae are only influenced in the water column(they do not have roots in the sediment), the Ac added to the filter is a reasonable method to remove such allelopathic compounds.

Ho = the null hypothesis, Ha= alternative hypothesis.
If we test the hypothesis that suggest that adding AC will induce algae(our Null hypothesis: Ho), then we would test that with the assumption that we will get algae and see that was true or not.

This is a reasonable assumption for this hypothesis.
If we test this and we do not get algae, then we reject the null and accept Ha: that algae are not repressed/inhibited by allelopathic chemicals.

We have falsified the null.

Put into real words rather than stat speak: we falsified the hypothesis that allelopathy inhibits algae.

I'm not saying what causes algae to be repressed etc, only in this specific case, what it cannot be. By ruling out each possible cause one by one, we get progressively closer to the cause/causes(there always might be more than one).

When you know you no longer have to worry about that one cause, then you can better focus your interest, research, investigation etc on other "potential tentative "causes. Answering one question leads to a dozen other possibilities.

In both test, we do not get algae, so we can rule out in a healthy run planted aquarium that allelopathy is not the cause for algae repression.



It's pretty good at allelopathic compounds based on the research that's available.
Nice large secondary compounds are taken up easily.


Because based on the known research on allelopathy where the effects are significant, AC does remove those chemicals effectively. Copper, as far as I know, is not a secondary allelopathic compound produced by plants and thus is a poor comparison. AC is very good at removal of a very wide type of organic compounds as well as a few inorganics.


Well, folks enjoy saying that, however, we can and do isolate things and aquariums are often used for this purpose in aquatic research. Then we take those models and see how well they apply in the field. Aquariums can be highly controlled and have parameters ruled out. We also use controls to account for the other complexity then do our treatments.

Here's the rub about allelopathy and an argument Ole never made nor I've read elsewhere ever:

What are the odds that all 300-400 species of aquatic plants all have the same intensity and type of algae repression due to allelopathy?

That is the observation that planted aquarist see.
We see this with a huge range of variation.
We see, over an extremely wide range of plant species, genera, families, orders, phyla........even...that there is no algae under good environmental conditions.

I'll tell you the odds: Billions or more to one.
Maybe higher.......


Well, you do not need to isolate it. There's no evidence to suggest that AC is ineffective at removal of the allelopathic chemicals.

It really becomes too far removed form the reality of the typical planted aquarium where we see the observations with a wide range of plant species combinations and routines.

I think I and many other researchers have a hard time when folks do alllepoathic studies and dump various mashed up crushed organism chemicals on other organisms in little test wells. That's far far far from realistic and does not tell you a thing about what occurs when these organisms are living (Which is what we are interested in).

In the Ecology of the Planted Aquarium, Tables III-1 through III-4 are meaningless in natural living systems. They are for extracts only, not for live living organisms. They offer no support for the argument.

You crush up and mash anything and add high concentrations of the extract to critters in test wells or agar plates etc, I can promise you can get inhibition as well!

Those test where no looking at living systems or ecology, they where looking for chemical extracts to kill algae or plants etc.

Even a cell has subcellular bags of toxic chemicals inside it, but does just fine. If you grind up these bags and place them on another of the same type of cell, you can kill the cell. The mere presence of those chemicals does not imply that the plant exudes them exogenously.

That is part of those tables that is not really made clear and leads folks to assume much more than what the tables really are able to say.


See the errors of those ways above......I'm not the only researcher who'd tear that implied argument to bits either.


They have done this for many species.
Mostly weeds..........


Some terrestrial plants do.........however, they do not have their chemicals continuously washed away and diluted either by the water that the aquatic plants live in. We also have good evidence that in terrestrial systems that alleopathic chemicals do play significant roles, sometimes very much so, and that AC works well as a control. Read the Gopal 1993 paper, it's long, but it's the best review on the topic. I'm not sure why or how allelopathy was given so much speculation in the Ecology of the Planted Aquarium.

After reading about allelopathy, knowing and having done pot test with various terrestrials, reviewing aquatic plant systems, having a wide range of algae related research, I do not get how you can conclude that much personally.

I think the speculation is mentioned and outlined clearly in most cases where it's made, but most hobbyists do not read that part

Regards,
Tom Barr

Maybe this is oversimplifying. But if carbon eliminates allelopathic compunds, and allelopathic compounds inhibit algae, we should see a pattern of algae blooms occurring shortly after carbon is added to a filter in a planted tank, and subsiding after carbon is removed. Not every tank, every time, but in general.