I am used to just using the term Ammonia, although this is as you say not completely correct. I will try to distinguish Ammonium/Ammonia as there clearly are a difference.Nice question!
First off, plants will use Ammonium (NH4+), not ammonia(NH3). In the biological process, plants will convert ammonium to nitrite by bacteria call Nitrsomonas. Nitrite is usually very quickly converted to nitrate, by more agressive bacteria, Nitrobacter. Nitrite is known to be toxic to terrestrial plants, even at low levels. The same is true for aquatic plants. So plants can utilize nitrogen either in the form of ammonium or nitrate. Some plants have a preference of one over the other, but most don't.
For sure!I may be out on a limb here, but I feel pretty confident that the plants can take up ammonium without help from bacterias.
Maybe, but this oxidation will probably always take place at some level no matter how much the plants uptake. Remember that the plants are not absorbing the ammonium all at once.And that ammonium to nitrite convertion only happends by bacteria if there are not enough plants to absorb it.
I wouldn't argue that plants cannot take up nitrite, but I will say that at some level it will become toxic, just as very high levels of ammonium and nitrtate can become toxic in plants. I'm sure its the case that it takes much less nitrite to lead to toxicity than nitrate or ammonium. Again, I'm basing most of this on terrestrial plant research and it gets kinda cloudy with submersed plants.The third point in this paragraph goes right to the core of the discussion I refered to.
In the link bgzbgz posted, there are a small section about it, and a graph (fig 3)
I'll just paste the section here, since this is what the debate revolved around.
Nitrite Uptake by Plants
Although plants can use nitrite as an N source, the pertinent question for hobbyists is- Do aquatic plants remove the toxic nitrite before the non-toxic nitrate? I could not find enough studies in the scientific literature to state conclusively that they do. However, the chemical reduction of nitrites to ammonium requires less of the plant's energy than the chemical reduction of nitrates to ammonium. (A plant must convert both nitrites and nitrates to ammonium before it can use them to make its proteins.) Thus, it is not surprising that when Spirodela oligorrhiza was grown in media containing both nitrate and nitrite, it preferred nitrite (Fig. 3).
As one can see, this suggests that nitrite may be benificial to aquatic plants, even though it is considdered poisonous to surface plants.
It may be a measuring error (maybee there were nitrobacters in the sample), and it may be that the Spirodela O. does not represent the typical aquatic plant. But there are something there worth to follow, and it would be nice to be more certain about this.
I have just ordered the book today.Diana Walstad's book covers some stuff on nitrite uptake by plants also. Take a look at that if you have it.
Seems like we are pretty much in tune.For sure!
I wouldn't argue that plants cannot take up nitrite, but I will say that at some level it will become toxic, just as very high levels of ammonium and nitrtate can become toxic in plants. I'm sure its the case that it takes much less nitrite to lead to toxicity than nitrate or ammonium. Again, I'm basing most of this on terrestrial plant research and it gets kinda cloudy with submersed plants.
I think this is kind of an academic question because on a practical basis if you add NH4/or NO2 as a one off fert then you risk toxicity to fish etc and NH4 spikes have been put forward by Tom Barr as triggers for algae growth.Hi
There was a litle discussion on another board (non english) about what the plants prefer to use as nutrition.
One view was that the plants prefered Ammonia over nitrite, but would use nitrate when the two former was exploited.
The other vie was that the plant prefer Ammonia, cannot use nitrite, but would use nitrate when there was no Ammonia. According to this view the nitrite might pe poisonous to the plants.
Now I hope to get more info on the subject, since there seems to be a lot of knowledge on this forum, I am trying here.
Are one of the former "statements" correct, or is it something inbetween?
I agree Brenmuk, I put those tabs in and then realized that they were made with NH4+. If I add anymore, I will get the proper tabs, but everything is doing fine. So if it ain't broke don't fix it i guess. I just wanted to relay my experience that I probably messed up a bit by changing so much water cause my PH was 6.5 which means the Total Ammonia reading was relativley harmless. Even after changing 70% of the water the Total Ammonia reading was exactly the same due to the tabs still leaching into the water, so what is one to do. The next day it was fine.I think this is kind of an academic question because on a practical basis if you add NH4/or NO2 as a one off fert then you risk toxicity to fish etc and NH4 spikes have been put forward by Tom Barr as triggers for algae growth.
If you add NH4/NO2 on a regular basis your biological filtration will adapt to the higher levels and produce more NO3 (or your plants will get it first) but why bother risking toxicity/algae?
If you want to add extra NH4 then just add extra fish - they produce it constantly .