# Allelopathy in aquarium plants



## timwag2001 (Jul 3, 2009)

i dont think that anyone has any concrete evidence on allelochemicals affecting either aquatic plants or algae. some things that have been said are anacharis and algae, sags and vals, and some others too. 

check this thread out http://www.aquariacentral.com/forums/showthread.php?t=218224&highlight=allelochemicals


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## plantbrain (Dec 15, 2003)

ua hua said:


> I have been reading up on allelopathic plants and find this a very interesting subject that still is really being researched. I have experienced this firsthand with plants in the garden and was curious how certain plants could do this in our aquariums. For those that are not familiar with allelopathy it is when plants release chemicals to out compete or kill plants that grow around them. I was curious if any of the known plants that are kept in the aquarium hobby are known to be allelopathic. It could be helpful to know if a certain species was known to be allelopathic before you try planting it in your aquarium just to have it kill a plant you put next to it. From what I have read certain plants are known to affect only some plants. For example the Manzanita has allelopathic defenses against herbs and grasses. This is a subject that could be very useful in organic farming if agriculturalists could indentify certain chemicals which could be used as natural pesticides and weed killer. Either way this is something I find very interesting and worth reading up on some more.


Well, it's not really being researched that much and it is extremely hard to prove in a real system in aquatic wetlands.

Plenty of lab type test that really lack good controls.
Or bioassays where they grind up plants etc, and add extracts to test wells.

Not particularly realistic.

Even if you ground up a plant, and added it back on itself(same species), many will have inhibitions. All the aquatic systems have had lots of trouble demonstrating it, plenty of criticisms on edit review boards etc.

While manzy might seem allelopathic......maybe it's just using the resources vs adding anything that is allelopathic, perhaps it's some bacterial indirect changes in the rhizosphere? Maybe it's blocking the light for lower growing plants? Maybe the taller pines are inhibits and competing?

Aquatic plants compete certainly, I just see less reason for them to do it vs say........growing faster.......bolting for the surface etc..........., the pay off is better. Aquatic plants can also move around a lot faster than any terrestrial plants other than some parasitic plants/bird vectors.
Terrestrials have to stay and fight.

Manzy is a serious competitor for Pine in National logged forest. You can see dramatic differences with exclusion over long time frames in the tree rings before and after.

Whether this is due to allelopathy, I'm not certain. 
Folks like the idea, but I doubt there's going to be any breakthroughs in aquatics anytime soon.

Still, never seen any evidence of this in 300+ species grown together, other than competition for resources(CO2 mostly). Adding activated carbon, doign large frequent water changes provides a control vs not using these 2 methods.

No one has really seen anything to date.

Regards, 
Tom Barr


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## plantbrain (Dec 15, 2003)

ua hua said:


> I have been reading up on allelopathic plants and find this a very interesting subject that still is really being researched. I have experienced this firsthand with plants in the garden and was curious how certain plants could do this in our aquariums. For those that are not familiar with allelopathy it is when plants release chemicals to out compete or kill plants that grow around them. I was curious if any of the known plants that are kept in the aquarium hobby are known to be allelopathic. It could be helpful to know if a certain species was known to be allelopathic before you try planting it in your aquarium just to have it kill a plant you put next to it. From what I have read certain plants are known to affect only some plants. For example the Manzanita has allelopathic defenses against herbs and grasses. This is a subject that could be very useful in organic farming if agriculturalists could indentify certain chemicals which could be used as natural pesticides and weed killer. Either way this is something I find very interesting and worth reading up on some more.


It would be great if .............it worked and you can show it really does and confirm it.

EPA has a fast track permitting program just in case it does BTW.

Regards, 
Tom Barr


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## ua hua (Oct 30, 2009)

Thanks for the replies. While this is a fairly new topic to me I find it very interesting that plants may have evolved to have these defenses. I understand that this may or may not really happen or it could simply be other factors such as a plants root system outcompeting a plant or blocking the light from reaching a competing plant. I don't understand why there is some people that don't believe allelopathy to be a plausible theory. Is it because it is hard to prove lab results because it is not realistic conditions or because they can't pinpoint a certain chemical compound that is released by the plants. While I'm by no means an agriculturalist or ecologist I find that this could have a huge impact on many different areas if it could be proven. Where I live they have to spray for Phragmities on a yearly basis along the Platte River and it would be much more beneficial to the enviroment if a natural remedy could eliminate the invasive species rather than polluting our waterways with pesticides.


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## plantbrain (Dec 15, 2003)

ua hua said:


> I don't understand why there is some people that don't believe allelopathy to be a plausible theory.


It's not a question of belief, it's a question of the evidence and results.



> Is it because it is hard to prove lab results because it is not realistic conditions or because they can't pinpoint a certain chemical compound that is released by the plants.


Finding the chemical is not the issue, showing that the chemical does act in some way in natural systems is the problem. Grinding it up, extracting etc.......none of that replicates a natural growing live plant exuding chemical defenses. Roots influence the soil bacteria and chemistry in the soil, which in turn could be why the effect is seen, not anything to do with allelopathic chemicals.

There are other problems as well with testing/methods. This is just one example.



> While I'm by no means an agriculturalist or ecologist I find that this could have a huge impact on many different areas if it could be proven. Where I live they have to spray for Phragmities on a yearly basis along the Platte River and it would be much more beneficial to the enviroment if a natural remedy could eliminate the invasive species rather than polluting our waterways with pesticides.


How about a biocontrol agent instead that can eat just that weed?
They do that for Purple loosestrife. Worked pretty well in some areas in CA.

Why do you think there is a weed issue with Phragmities in that region?
Water stabilization for human flood controls, irrigation etc.......leads to stable habitats for weeds adapted to short growing times for good habitat. So they grow like mad all year long almost.

If the water regime was natural, they get washed away or flooded and die back, likely would no longer be a weed issue.

So maybe it's a human issue and not a weed issue?
Think about that. There are solutions and we should look for new ones, but I do not think they have been show effective for allelopathy in aquatic plants.

It's not due to "not looking" either.
Same for Biocontrol(less $$$ to made there vs a chemical that can be made and sold).

Economics of research, getting the product to market and passed the EPA and the state pesticide control boards cost a lot of $$ either way.

Typical herbicide is 10-20 million and then 2-3 million to bring it into CA for example. Allelopathic chemicals have a faster track and are cheaper........but........it's still millions and millions and they rarely are effective enough economically to control or manage weeds(they have to be really effective to worth while economically). Cost = benefit.

Would you make such a chemical if you put in 20 million and then could only sell 200,000$ worth a year? It's not so simple.


Regards, 
Tom Barr


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## ua hua (Oct 30, 2009)

Thanks for the replies Plantbrain. It is nice to get a straight forward answer from a knowledgeable source. I do believe that the invasive weed probelm in my area is more of a result of human actions whether it be from irrigation for farmlands or diverting the natural flow of river systems. I know I may not be realistic when in comes to finding an alternative to harmful chemicals especially in a world where money talks and bs walks, but in the perfect world in would be nice. Thanks again for the replies, I learn a little more everyday on this site.


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## snausage (Mar 8, 2010)

In 'Ecology of the Planted Aquarium,' the author has a chapter discussing allelopathy. I didn't read it very closely, but she claims that valisineria will kill certain types of plants via allelopathy.


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## plantbrain (Dec 15, 2003)

ua hua said:


> Thanks for the replies Plantbrain. It is nice to get a straight forward answer from a knowledgeable source. I do believe that the invasive weed probelm in my area is more of a result of human actions whether it be from irrigation for farmlands or diverting the natural flow of river systems. I know I may not be realistic when in comes to finding an alternative to harmful chemicals especially in a world where money talks and bs walks, but in the perfect world in would be nice. Thanks again for the replies, I learn a little more everyday on this site.


Well, the weed got there somehowroud:
Then it grows really well because we gave it a great place to grow.
Then these folks call me or someone up and wanna fix this issue.

Maybe a farmer who's crops are being threatened, maybe a State Biologist who's concerned of a native species being over run, or a rare species or habitat for native rare species..........maybe it's "Ducks Unlimited" who love to hunt water fowl or all these groups wanting to address the same problem.
Then maybe there is a group of urbanites who think they are adding "poisons to the water and files a lawsuit to try and stop any chemical control and thus stops any control of the weed which over runs the natives and wipes out the 10 years worth of control and $ spent on trying to eradicate the weed.

Believe me.........this is often how this stuff goes down.

There are MANY stake holders and groups with interest in these wetlands/riparian strips, and folks like you are an asset cause you care.
These problems are not so black and white, and researchers/scientist are often stuck in the middle. Often times, no one takes our advice, but only wants to use us to support their own agenda. Poor leadership is what we call it. But.....in farm systems...........most of them like us and it's interesting to find a solution with all these trade offs. My attitudes have changed a fair amount as I learned more and more about the entire process and dealt with some of the issues first hand.

Dealing with weeds is a lot of labor manually, chemically, many folks hate it, but there are few alternatives. I specifically work with those alternatives.
But that's not the hobby.........that's weed management.

Regards, 
Tom Barr


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## mistergreen (Dec 9, 2006)

If you want to manage weeds, you'll have to eat them or at least get a herd of moose.


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## plantbrain (Dec 15, 2003)

snausage said:


> In 'Ecology of the Planted Aquarium,' the author has a chapter discussing allelopathy. I didn't read it very closely, but she claims that valisineria will kill certain types of plants via allelopathy.


It's not been demonstrated in a natural system.
Vals can use bicarb, maybe it's just the fact they can grow well under limiting CO2 and the other plants cannot? Maybe it's they have better light use efficiency than the other species? Maybe indirect due to rhizosphere bacterial changes btw species in the root zone?

Hard to say.

You can devote a chapter...........speculate(which is about all she is doing there), but it does not illustrate it occurs, there's a large table with listed of test wells results, none of which supports anything to do with an intact live plant in an aquarium.

I'd say light use, CO2 competition etc..play larger roles and these we can measure.............

Few have measured differences btw submersed plants and CO2 competition.
You can believe, or you can test and see, try different things to see if this claim holds true or not.

I've found no evidence that it occurs in a single tank.
Every case, including vals or sag's as well as many others, have failed in the aquariums I've had to show any signs under controlled conditions.

If you have poor controls and cannot confirm things like CO2 well, or try removing the chemicals of interest etc.........you really cannot say much.
You can speculate, but that does not support the results....because there are not any.

In aquariums..........or in natural systems(at least ones with good controls).



Regards, 
Tom Barr


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