# Nutrient Uptake: root preferred?



## MiamiAG (Jan 13, 2004)

OK, much debated, often speculated...

Do plants have a preference to take up nutrients via their roots or via stem/leaves?

I recall reading that plants with an extensive root system will prefer to take up nutrients (especially some nutrients) via roots as opposed to the stem/leaves. Of course, this is provided the nutrients are available in the substrate solution. Of not, they will take them from the water column.


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## Anonymous (Jan 13, 2004)

A number of research papers(See Journal of FW biology 2001-2002) suggest when the concentration on water column nutrients are sufficent, there is no significant growth impact by even removal of the roots.

In many/most systems, the water column nutrient levels are below the limits for sustained growth(but maybe fine for 1-2 months of the year etc).

The plants have to have some source of nutrients ultimately for growth, so the plant will get it from the substrate if none is available in the water column. The plant does not have a choice if there's nothing in the water column.

Whether this is a "preference" or not in the literature seems to be confused since many assume since most plants get their nutrients mainly from the substrate in nature, that this means that is what the plant prefers.

That does not appear to be the case based on controlled studies............
Nor my own trails with water column dosing Crypts, swords or otherwise.

I will say that having nutrients in both sources, especially iron in the substrate, has helped significantly. 

As far as adding macro's to the substrate when the water column is rich in the nutrients: I have not found any growth differences.
The literature supports my study as well as do several others that used things like jobes etc.

It's when you want to remove nutrients from the water colunmn below a plant's threshold that the substrate effects become significant.

Both sources of nutrients work and you need some from both sources for good healthy plant growth IME no matter what. It's also rather hard to have a plant tank without any influences from the substrate or the water column. Almost all tanks have some of each playing a significant role.

Regards, 
Tom Barr


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## MiamiAG (Jan 13, 2004)

Tom,

You bring up interesting points.

As you know, many of us rely on old studies brought up by a plant physiologist via the APD. His point was the aquatic plants had a preference to take certain nutrients via the root system if it was available.

I have not read those studies, but I would be interested to know what impact this would have on the plants energy reserves. In other words, does the plant need to work doubly hard to uptake nutrients via the roots and then must rely on transport to bring the nutrient to the leaves for photosynthesis? Or, is it easier for the plant to take the nutrient through the stomates and not have to transport it a long distance? Is this plant specific?

In the end, it is important to consider the take away for planted aquarium use. Is it preferable to have the nutrient in one place or the other or in both? I am a very strong believer in a nutrient storehouse concept in the substrate. Therefore, I try to make sure it is available there. However, I guess you always want the back up of having in the water column as well just in case.


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## plantbrain (Jan 23, 2004)

Well there are a lot of aquatic plants but when folks generalize, they often lump in other terrestrial plants that have recently come into the hobby that are not submersed for long periods ...if at all.

If a plant has to transport something from the root or the leaf, first it has to take the nutrient in across a membrane. There's an energetic cost associated with that. There's also transport issues. 

It takes energy to get a nutrient from one place to the other and to change it's form for transport and unloading in some cases such as iron. 

Iron is one nutrient I have to argue for is best in BOTH places, rather than just the water column. I think overall, most people if they are critical with their rotuines will find they can grow Amano quality with fish food/water column dosing and some iron in the gravel.

I'm not too sure about the impacts of the others besides Fe but it seems less important overall than any others. I've added jobes and other macros to substrates and when the nutrients are fine in the water column, no improvenment in growth was noted, this was also supported by a number of other folks who kept good water column dosing at the time of the macro substrate additions.

The old method of putting everything in the substrate and nothing/little in the water column _also_ works and there's no reason why it should not.
Some seem to assume that this in direct conflict with water column dosing of macros and it is not. 

But it still has the same nutrients available to the plants and provides perhaps for a little slower growth(not a bad thing in some cases). 

Past issues(algae) with that method were often from using urea and NH4 based ferts.
But poor growth was often seen regardless of base ferts vs a water column dosing routine if you apply a pure system which is never the case in anyone's tank test I've ever seen in the hobby.

Folks calim nothing added but then you find out they have a substantial fish load, traces are dosed, K+ etc.

You can try various combo's of macros in various ratios in both sinks(water column or substrate), but ultimately the nutrients wneed to come from somewhere, providing some in both places is not a bad idea it seems.

Some claim less algae when they add more to the substrate but these are not critical test by any means.

I've worked with the water column extensively and extremely nutrient poor substrates(which is how I got to know a good deal about water column interactions).

This makes for a good base to approach what works well in a substrate vs the water column.

Many aquatic plants do not have stomates BTW, eg Hydrilla, Egeria, etc.
They are only 2 cells thick. 

But back to your approach, both is best IMO. You gain little by having a pure water column with few nutrients. 

But pure systerms are exceedingly rare in both nature and in the hobby.
So when folks talk about their "new" system, little has changed in the last 50 years, they use both the substrate and the water column.

I did this same nutrient poor substrate approach with Flourite some 7-8 years ago. It really did much better with many plants with a number of routines vs sand or sand+ laterite.

Iron did play a significant role and there was slower, perhaps one could argue, more managable, growth with sand/laterite mixes. 

But I think a good goal: Have some NO3/PO4/Fe in the substrate, accreation of organic matter in the substrate, dose some NKP and traces to the water column also, you might be able to lean the water column more to get the desired effect but I think anyone can have Amano quality tanks by adding a little more or less to each sink of nutrients without any issues.

Having a back up in both areas will prevent any nutrients from running out.

I will say switch the nutrientr levels back and forth in either region is not good for the plant, it needs to have a steady supply no matter what, but still, having some in another sink is better than none at all.

Regards, 
Tom Barr


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## MiamiAG (Jan 13, 2004)

Thanks Tom.

You mention accreation of organic matter in the substrate. What do you mean by this? Would you recommend the use of peat or other organic to facilitate the nutrient uptake by roots?


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## niko (Jan 28, 2004)

This thread might be a good place to ask what does Amano do for water column fertilizing?

From what I read, his P and N are always 0 (or N of 0.6 at the most). 

How much and what exactly are his products that one sprays in the tank?

--Nikolay


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## MiamiAG (Jan 13, 2004)

Niko,

I'll answer in the Fertilizer forum.


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## hubbahubbahehe (Mar 29, 2004)

I've read that different elements have different preferences. Like N might be root preferred, while K is leaf preferred. CAn someone verify this?


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## Justin Fournier (Jan 27, 2004)

hubba, I assume your read this in Walstad. I read the same. I wonder if they are terrestrial plants like Tom mentioned earlier, or they are true aquatic plants. I can't remember the name of the plants used in the study, but seem to remember not recognizing them at the time.


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## hubbahubbahehe (Mar 29, 2004)

Hi Justin! yep! it's from Ecology, I don't think it's terrestrial though cuz how can terrestrial plants get N from their leaves?


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## Justin Fournier (Jan 27, 2004)

I was thinking along the lines of a Bog plant, but who knows. I would have to go look it up and I lent the book out to a friend. Just an idea....


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## Hanzo (Mar 9, 2004)

Great stuff, good reading on this early morning.

I have never tried anything but plain gravel for my substrat, but have been using a substrat heating cabel. This has worked wonders for me, but reading up lately I have been thinking about trying laterit in there as well. One guy over at the norwegian forum used laterit in the bottom, and then but a thin piece of cloths over it before he added the gravel. This keep's the laterit form mixing in with the gravel. I might try this.

Over time I guess all the organic stuff that gathers in my gravel plays a role in my thank, but for the first week, there was nothing but ferts in the water colum. I have conluded myself that most of the nutrients are best dosed in the water colum since this means less energy wasted for transportation. Are the nutrient broken down and changed somehow before it's being transported? If so, more energy wastet, right? I have been having a hard time keeping the iron level up, and so dosing some in the substrat might help, guess it's time to give this a try to.

Guess a big part of this hobby is the experiment behind it, and so I guess it's time for me to try some substrat ferts. Maybe this means my tank will be more forgiving when I mess thinks up and forget to check my tank parameters for a while


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## gpodio (Feb 4, 2004)

A recent expriment in Europe using crypts grown submerged clearly showed the benefits of substrate fertilization. Their results did show preferences in location for certain elements, some were preferred in the substrate while others in the water. I plan to translate this long article when I get some spare time, it should be of great interest to many of us.

Personally I wouldn't run a tank without fertilizing the substrate, it's something I've been used to doing for many years regardless of the type of tank. In my low light tanks I fertilize the substrate alone, only in my high light tanks do I also fertilize the water column. I guess that's the opposite to many I hear but it has worked for me for a long time. Ideally though, if you have nutrients available in both places, the plants will obviously be able to choose where to get each element from based on ease of uptake and energy required to process each element. I'm sure that would be the ideal environment.

I think Walstad is right on track with this one. The tests she wrote about showed the same preferences, at least with the couple of plants that were used. I guess there is always the possibility that different plants have different preferences, but like I said, her tests results were consistant with the recent tests done on crypts.

Regards
Giancarlo Podio


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## Hanzo (Mar 9, 2004)

> A recent expriment in Europe using crypts grown submerged


Yes, but Crypt's are more of a bog plant, right? So I guess it's more dependent on it's rot than many other plantes, or am I wrong in this asuption? It would be nice to see the same experiment with Ludwigia Arcuata or something like that.


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## hubbahubbahehe (Mar 29, 2004)

Hanzo said:


> > A recent expriment in Europe using crypts grown submerged
> 
> 
> Yes, but Crypt's are more of a bog plant, right? So I guess it's more dependent on it's rot than many other plantes, or am I wrong in this asuption? It would be nice to see the same experiment with Ludwigia Arcuata or something like that.


"dependent on it's rot?" what do you mean by that?

In my experience, I have found that stem plants will do just fine in a plain gravel substrate with water column fertilization. It's the substrate fertilization for swords and crypts that really work wonders.


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## gpodio (Feb 4, 2004)

I think you will find that most of the plants we use in our tanks are either bog or naturally found partially or even fully emersed. But we can't use nature as a guide here, many of these plants will revert to their basics when placed under water and change the way they uptake nutrients. Their surroundings dictate what they have available, it's not necessarily the ideal growing environment. Infact, most of us grow plants faster than nature does. Further, even real aquatic rooted plants in nature are forced to use the substrate as the major nutrient source as the water is often very clean and lacking in most nutrients.

Plants adapt so we can only expect different growth rates when doing these tests. In none of the experiments I have seen were any plants killed or showed any significant signs of deficiencies, just different growth rates, root development and some quality differences. It's not a break it or make it condition, people grow nice plants both ways, these are really just final tweaks to an already healthy environment. If you can get an extra inch per month you have proved something, not necessarily made a world of a difference though, nor have you necessarily imited nature in any way, actually you probably strayed away from it even further.

Giancarlo Podio


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## hubbahubbahehe (Mar 29, 2004)

GP, I think you brought up a very good point ...that we grow plants faster than nature. That made me think, co2 is rarely at 30 ppm in nature correct? But I'm kind of thinking that with constantly flowing water that the nutrients come and go all the time and the plants take up what they can... Do most plants grow in stagnant water or flowing waters?


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## Hanzo (Mar 9, 2004)

Not sure if it's my lousy spelling or my intention your not getting 

My point is that crypt's and swords are mostly bog plants, and as fare as I know, mostly grow emersed, am I right? If this is so, it would make sense that they are more in need of the root system than normal stem plants.


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## hubbahubbahehe (Mar 29, 2004)

Hanzo said:


> Not sure if it's my lousy spelling or my intention your not getting
> 
> My point is that crypt's and swords are mostly bog plants, and as fare as I know, mostly grow emersed, am I right? If this is so, it would make sense that they are more in need of the root system than normal stem plants.


Absolutely, I totally agree with that. They are often referred to as "heavy root feeders."


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## Phil Edwards (Jan 22, 2004)

Hanzo,

From the photos I've seen it looks as though crypts grow in and out of water in approximately the same amount amounts. 

As for nutrient uptake, I would guess that plants are more likely to take up Ammonium through their roots and Nitrate from their leaves in an aquatic system because NH4+ is likely to bond to reducers in the substrate while NO3 is easily drawn out of a substrate. Furthermore, going on the assumption that most water is clean (which isn't nearly as true as we think) the plants will have to use their roots to take up the nutrients they are unable to take up through their leaves. In eutrophic conditions plants are quite likely to take up nutrients through their leaves and can do quite well by doing so.

Best,
Phil


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