Allelopathy

handimn1

Junior Poster
Mar 7, 2006
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I was wondering if anyone has experience with Allelopathy, the defenses that plant protect themselves with and how it affects other plants! I am reading a book by Diana Walstad and she has a chapter in her book about it!
 

Raul-7

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Sep 8, 2005
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Re: Allelopathy

It seems Tropica had a great article on it aswell.

www.tropica.com

Under the tab Aquaristic, it's an article by Ole Pedersen who refers to Diana's experiments.

Pedersen said:
Personally, I do not see much ecological relevance in these kinds of experiments. At best, they may be used to look for potential candidates of true allelopathic behavior because the studies, after all, demonstrate that the plants contain toxic compounds. However, many of these studies take the conclusion much too far and recommend using the plants for aquatic weed management or algae control without the necessary documentation for allelopathic behavior in nature.

It would be interesting to see what Tom has to say about this.
 

fosteder

Guru Class Expert
Feb 3, 2005
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Rochester, NH
Re: Allelopathy

I have heard Tom say that Allelopathy (in terms of keeping algae under control in our aquariums) is unproven malarky....maybe not his exact words. :D
 

Tom Barr

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Jan 23, 2005
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Re: Allelopathy

Raul-7 said:
It seems Tropica had a great article on it aswell.

www.tropica.com

Under the tab Aquaristic, it's an article by Ole Pedersen who refers to Diana's experiments.



It would be interesting to see what Tom has to say about this.

Ole and every other aquatic botantist says the same thing including myself.

Funny how we all agree but the hobbyists keep thinking they might have a chance.

Regards,
Tom Barr
 

Tom Barr

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Re: Allelopathy

Allelopathy has several issues to overcome to shown to occur in any signifcant way in our tanks, which as Ole suggest is much different than all the presentations that Diana is suggestion.

Diana does not why the supression of algae occurs in her tanks, but she speculates and suggests it's possible. Ole and myself as wella s Tropica do not agree with her.

We have test kits, methods etc and will use them.

Main issues:
1. Adding the extracts of plant compounds on small test wells, petri dish plates are hardly the same as natural release in the water column. Few plants release foliar allelopathic compounds, most all of the evidence comes root mediated compounds, which, as we well know...........is not where algae grow:) There has never been a documented case of this occuring in any natural system. But.......if it does occur , it is very subtle.
As such, it most likely cannot play a signicant role in our tanks.

2. Are all the compounds the same? In her book she details some of the compounds and their differences from various plants. We have nearly 300 species available. What are the odds that all the compounds are all the same and produce the same effect in all tanks with good healthy plants?
Virtually none.

3. Simple experiments. Add activated carbon to the tank filter etc. This removes such compounds like it does tannins. You may also do huge water changes frequently to produce the same removal effect. If this was significant, we would see algae occur after a large water change in a CO2 enriched tank, or in a non CO2 tank with the activated carbon.

But we don't.................we do see algfae if you do water changes a lot in a non CO2 tank, but that is due to CO2 enrichment from the tap water once a week etc then back down again to very low levels of CO2 for the remaining days of the week, this favors algae, but has nothing to do with allelopathy.

If you look at this from only a non CO2 method, you might conclude allelopathy does occur since frequent water change can induce algae whereas not doing them reduces algae over time.

But is this effect really allelopathy or is it something else?
I've suggested the CO2 rich tap water as a reason as an alternative that much better explains the algae species obvserved when you do a frequent large water change routine on a non CO2 tank. The species induced tend to be low CO2 algae found in CO2 enriched tanks.

This also better matches the observations for all tanks, not just non CO2.
Stable CO2 levels are the key, not so much high or low, just no yoyoing back and forth.

The non CO2 tank grows slow and the CO2 levels are stable and are very low. This also limits algae, not just plants.

Regards,
Tom Barr
 

imatrout

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Apr 4, 2005
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Re: Allelopathy

I've had Hydro. Polysperma (Sunset) growing like a weed in my 150. There it grows 6 - i8 nches per week and the leaves ar 2-3 inches long. I put a sprig in my 1.3 gallon pico tank and there it grows very slowly and stays proportional to the size of the tank. I looks just like the original plant, but the leaves are at max 1/2 inch and new growth looks to be in the 1/4 - 1/8 inch leaves. It grows proportionally and even turns "Sunset" in color. It is a perfectly proportional (tiny) version of the original plant it was cut from. I can only attribute this to allelopathy. Any other ideas why this happens?
 

Tom Barr

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Re: Allelopathy

Nutrients, actual space(plants can sense if they touch something else), lighting is another big factor, flow....time, do you trim it as often as you might if the tank is 20" vs 10" tall?
I don't.


Regards,
Tom Barr
 

imatrout

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Apr 4, 2005
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Re: Allelopathy

Actually, in the pico tank, I have never trimmed it in 2 months and it is only 2-3 inches tall. It is healty and growing, but slowly. I'm amazed by this....
 

Raul-7

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Sep 8, 2005
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Re: Allelopathy

It's probably due to light and nutrients more than anything else.
 

imatrout

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Apr 4, 2005
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Re: Allelopathy

Raul-7 said:
It's probably due to light and nutrients more than anything else.
Isn't that what allelopathy is all about? How plants protect themselves for changing or harsh environments or being out manuevered by other plants and animal? The little tank get the same nutrient dose as the big tank however it sustains itself on natural light.
 

Tom Barr

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Re: Allelopathy

Unless you are sure about those nutrients/light, CO2 etc, and there's no real evidence in situ treatments work........and the effect is due to allelopathy.

If you believe it is, try adding activated carbon, you should see algae, better plant growth etc.

The other thing you can do, use just one species of plant.
If it grows smaller in the pico than the other larger tank with other plant species, that would be more suggestive that allelopathy enhances growth.............

I suppose you could attempt to argue for self allelopathy, that's even worst than the orginal hypothesis though :(

Is the lighting different in a pico vs the larger tank?
Is the distance from the bulb the same? Same age? Same substrate? Similar filter? Same flow? I can go on and on, these can and do effect plant growth.

But the real issue was about algae and plant interactions........not plant- plant interactions. AC will address the chemicals in plant - plant allelopathic effects.



Regards,
Tom Barr