# Do aquatic plants use roots to feed?



## Centromochlus (May 19, 2008)

> I know there are some plants that get much of their nutrients from whats in the water alone. But are there not plants that also take up nutrients by roots?


Sword plants are huge root-feeders, as well as a lot of stem plants in general. Almost all plants take up nutrients through their roots; some just more than others.



> I was on another forum and many of them are under the impression that you don't needs plant substrate and that plants don't needs any root feeding. in fact someone said root feeding plants is a myth.....


I'm curious as to who these people are and what forum they're from... IME, a good substrate is one of the most important aspects of a planted tank. Whoever fails to notice a difference in plant health after changing from sand/plain gravel to a plant-specific substrate is obviously lying.




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## Snowflake311 (Apr 20, 2011)

Thank you so I am not crazy. This topic is why I don't waste my time on the other forum any more. I feel here I learn a thing or two.


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## echoofformless (Jan 1, 2008)

My input on this topic is that you can not generalize anything in the world of biology. Each plant you mean to keep in your tank has unique requirements. Consider that many plants such as floating plants, mosses, algaes and ferns do not require any substrate whatsoever. 

Now consider the differences in plants that like substrate. Some, such as many stem plants, can live without a substrate for years. Others, such as crypts and swords need an extremely thick, very fertile substrate for their long, deep roots. Some plants (swords and hairgrass in particular) prefer a sandy substrate while others might like a more coarse sand or even a gravel. 

Every species also has its own unique lighting and feeding preferences. Some are even picky about temperatures...or pH...or hardness. Some will thrive on neglect. Others will require constant attention. 

Think about the diversity of biotopes in the world. Think about how many different environments all of these plants have adapted to. In order to make general statements, we must do so only when we have gathered species that come from similar environments. 

Finally, a word about these supposed "plant specific" substrates. They're a lot of bunk. There, I said it. A highly experienced aquatic plant enthusiast denying the usefulness of plant substrates except that sometimes they look nice. I have kept countless systems in my life, and never have I seen any benefit to the untold amounts of money I spent on things like Flourite. My heavy root feeders have done just as well in plain sand with root tabs as they have with "plant" substrates. Plant substrates are really just a lot of money for nothing. And I am far from the only hobbyist who will say this. The only substrates that really do have inimitable benefits are soil substrates, but those are only for the daring.


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## photogdude (Oct 27, 2010)

echoofformless said:


> My input on this topic is that you can not generalize anything in the world of biology. Each plant you mean to keep in your tank has unique requirements. Consider that many plants such as floating plants, mosses, algaes and ferns do not require any substrate whatsoever.
> 
> Now consider the differences in plants that like substrate. Some, such as many stem plants, can live without a substrate for years. Others, such as crypts and swords need an extremely thick, very fertile substrate for their long, deep roots. Some plants (swords and hairgrass in particular) prefer a sandy substrate while others might like a more coarse sand or even a gravel.
> 
> ...


What he said


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## mistergreen (Dec 9, 2006)

Plant feed where there are nutrients whether in the water column or substrate. Having nutrients in both would be ideal.


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## plantbrain (Dec 15, 2003)

mistergreen said:


> Plant feed where there are nutrients whether in the water column or substrate. Having nutrients in both would be ideal.


+1
Common sense really, you can do test and cut the roots off, just like uprooting and replanting the tops for most stems, or trimming the roots off a sword plant.

Without roots, it's sort of difficult to feed from roots .........no????

:icon_roll

and yet we do it..........

Overall, sediment + water column is the best more synergistic method, and most everyone does it anyway, whether they bother to add more in one location vs another, they still have some in each location, only the ratio or richness of the location varies.



> I was on another forum and many of them are under the impression that you don't needs plant substrate and that plants don't needs any root feeding. in fact someone said root feeding plants is a myth.....


I've heard claims of the reverse, which baloney, but not this one before. Crazy talk, "athletes mouth" disease.

It is true that plants do not "need" sediment ferts, but the water will still supply roots with some ferts from above, and vice versa and the combo provides better easier growth overall. Do not fall for "either or" baloney. 

Even terrestrial plants can take up most of their ferts via the leaves/stems etc, fertigation works this way and supplies the growing method for most ornamental plants sold in the USA.

The pots only have sand and bark in them.


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## audioaficionado (Apr 19, 2011)

+2

I fertilize my garden with both soil root ferts and foliar spray ferts. Why not my planted aquarium also? Both are useful IMNSHO.


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## Snowflake311 (Apr 20, 2011)

On this other fourm someone would ask "why is my Sword plant not doing well?" I would say try adding root tabs. Only to have other people say they don't need that. 

So for good plant growth it would be best to add nutrients to both the Water and the substrate right? Of corse depending on the type of plants and it's needs. Because I understand that plants like Riccia or even Water sprite get all they really need from the water. 

So it is safe to say that there are plants that do need nutrients in the substrate?


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## defiesexistence (Sep 13, 2010)

Snowflake311 said:


> So for good plant growth it would be best to add nutrients to both the Water and the substrate right? Of corse depending on the type of plants and it's needs. Because I understand that plants like Riccia or even Water sprite get all they really need from the water.
> 
> So it is safe to say that there are plants that do need nutrients in the substrate?


Just like terrestrial plants we grow, plants absorb nutrients through the leaves/stems (like foliar spray), and their roots, so both the leaves and the roots will absorb nutrients. Water sprite is not a floating plant, which means it will benefit from having substrate. Stuff like duckweed is, and gets all its nutrients from the water column.

Very safe to say. I read a statistic that aquatic rosette plants absorb up to 80% of their food from their roots. Not sure how exact that is, but imagine how bad it would be if they didn't have substrate so their roots got that 80%. Roots are vital. Without healthy roots, it is pretty much impossible to have a healthy plant.


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## plantbrain (Dec 15, 2003)

I've not seen any studies that suggest rosette plants vs stem plant differences in root vs water column uptake. Often times, it's just a matter of some nutrients being somewhere, rather than any real preference.

Many hobbyists seem to equate large root systems with preference.
This might seem like an obvious correlation.

But.........the roots are often storage organs in these SAME species(Crypts and Swords most certainly) and these same plants grow in amphibious conditions, so large root systems will be required once the water recedes, the large roots anchors the plants physically.

None of which has much to do with uptake preferences.
Virtually all the reference research suggest that K+ is taken from the water column. Other species, perhaps PO4 from the soil.

But the concentration of these ferts in the pore water in sediments is much greater often times. Concentration drives uptake, so concentration, not so much location is one of the larger factors.

It makes little sense to state things based solely on what "feels right" :icon_evil

Few hobbyists actually have researched in any depth nor have tested critically any of this stuff. We trim off roots all the time, do you see a huge difference?

I do not.

Folks add a root tab, they see a difference, but this may have simply been a limiting factor, or they did not dose the water column consistently. Either way, if you dose the sediment and the water column, then it does not matter, you have both possible cases covered and some flex if you forget to dose the water.


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## thewife (Jan 26, 2011)

You have to look at all parts of an organism in terms of evolutionary adaptation. If Tropica proved anything...it would probably be that most available organic nutrients are not found in the water column. Whereas it's pretty clear that river etc. sediments are extremely rich. Human beings have been making use of that factoid since ancient Babylon at least. Despite the risks, floodplains are still in agricultural use for that very reason. In addition to that, most floating/mossy-ish plants don't require much in the way of nutrients. At least, I can't think of any offhand that do. 

One could therefore reasonably hypothesize that aquatic plants take up most of their nutrients through their roots UNLESS forced to do otherwise. Calcium and magnesium (and other) ions are probably mostly taken up through the water, since it's just dissolved rock and is more abundant there whereas the sediment is rich in organics. 

Extensive root systems on the other hand probably have more to do with the native strength of current than anything else - or even a mechanism to deal with some of the more aggressive herbivores.


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## Snowflake311 (Apr 20, 2011)

Thanks guys lots of great answers it really gets me thinking.


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## Chlora13 (Jun 20, 2011)

Wow, I am pleased to see we have some amount of scientific people in this community. First off, the one thing that irritates me is that people still think that land plants absorb nutrients through their leaves! Bogus the lot of it, and it's been debunked on several occasions. What really happens is the rain washes it off, and it soaks into the ground, and viola! your plants start to look better. As a horticulturist, and native plant community manager, this really gets under my skin! Roots take up nutrients and water, and leaves (and ever other cell in the plant) respires. Epiphytes or air plants yes, get their nutrition from the air and rain, but they still do not take it up through their leaves, they use their modified roots! if you apply a foliar nutrient to the water column, and it's deficient in the substrate, yes it will diffuse in through osmotic potential and your plant will take it up and look healthier etc. That is for aquatic plants though. 
Oh, and as for the sandy soil with root tabs, yes it works, but clay is the particle that nutrients and water adhere to. Hence why a sandy soil is infertile and dries out quickly, but a clay usually will be rich, and stays soggy for days! 
And as for the original question; Honestly it really depends, floating plants like duckweed never touch substrate and aren't designed to. Lilies need fertile substrate, because their roots were designed to be anchored to the bottom in rich muck. Rule of thumb, emulate where and how they live in nature, you can't go wrong with that.


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## thewife (Jan 26, 2011)

Chlora13 said:


> Wow, I am pleased to see we have some amount of scientific people in this community. First off, the one thing that irritates me is that people still think that land plants absorb nutrients through their leaves! Bogus the lot of it, and it's been debunked on several occasions. What really happens is the rain washes it off, and it soaks into the ground, and viola! your plants start to look better. As a horticulturist, and native plant community manager, this really gets under my skin! Roots take up nutrients and water, and leaves (and ever other cell in the plant) respires. Epiphytes or air plants yes, get their nutrition from the air and rain, but they still do not take it up through their leaves, they use their modified roots! if you apply a foliar nutrient to the water column, and it's deficient in the substrate, yes it will diffuse in through osmotic potential and your plant will take it up and look healthier etc. That is for aquatic plants though.
> Oh, and as for the sandy soil with root tabs, yes it works, but clay is the particle that nutrients and water adhere to. Hence why a sandy soil is infertile and dries out quickly, but a clay usually will be rich, and stays soggy for days!
> And as for the original question; Honestly it really depends, floating plants like duckweed never touch substrate and aren't designed to. Lilies need fertile substrate, because their roots were designed to be anchored to the bottom in rich muck. Rule of thumb, emulate where and how they live in nature, you can't go wrong with that.


IMO, I think it makes the most sense to dose organics in the substrate and traces, K+ in the column. That's how I do it...it's really too bad I don't have a control tank. Although, when you think about it aquatic plants are so versatile in their ability to adapt that setting up a control is kind of meaningless. You see people who are able to get great health/growth with all kinds of methods, so it's nearly impossible to tell what is "best." Not to mention that plants are notorious for crossbreeding and getting funky ploidy, etc. At that point, if one system fails for that person, or it just fails with a particular plant but everything else is fine...what was really the cause? A few extra chromosomes or a single nucleotide deletion can make a big difference. 

Then again, Eskimos are capable of living on fat and protein essentially alone. They seem fine...yet there's no reputable nutritionist on the planet that recommends that kind of diet. Food for thought.


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## Robert H (Apr 3, 2003)

I think it is a question what is more readily available. Plants always take the path of least resistance. Rooted rosette plants, plants with rhizomes, bulbs, tubers do store nutrients, but if the roots growing from the tubers come into contact with nitrogen or usable minerals they will uptake those nutrients quickly.

This is also why you often see people at fish club auctions who know absolutely nothing about plants or how to care for them, bring in a monster size sword plant that has been growing for five years in their 55 gallon tank with nothing but a 15 watt bulb and they say they have never once given the plant any fertilizer at all. The tank has been running for five or ten years and has accumulated a ton of nitrogen rich crud at the tank bottom which is like steroids for the sword plant. But he couldn't grow a stem plant in the same tank to save his life.

Happens all the time.



> Even terrestrial plants can take up most of their ferts via the leaves/stems etc, fertigation works this way and supplies the growing method for most ornamental plants sold in the USA.


I think I disagree with you there. I worked in a nursery, and I have bought tons of potted garden plants and they were all potted in manure and top soil. In fact Florida aquatic nurseries grows many of their aquatic plants above water in manure and top soil. All their Java fern is grown in rich, dark black top soil. There are also many plants whose leaves and flowers will burn if coming in direct contact with nitrogen.


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