Re: [compost_tea] chelate question for the chemists out there

From: <soilfoodweb_at_aol.com>
Date: Wed, 28 May 2003 01:43:35 -0400

Hi Paulette -

Phew! Do you have time for a course in plant physiology? I'll will try to give you a short course, but please get a plant physiology textbook, or even better, call your local college or University plant physiology instructor, and get the expanded version of these answers, if you are interested. My knowledge is limited when it comes to the insides of plants, plasnt strucutres, etc. But I'm pretty good at cellular metabolism questions, but I don't know everything.

> I was thinking about all this in terms of applying a chelated product such as chelated iron to a plant. The chelation process would have occured at the manufacturer's lab before I got the product. Many chelated iron products use EDTA but I've also seen lignin as the chelating agent.

Check whether the chelated material you want to apply is approved for use by organic growers. Check with an organic-certification group like the Organic Growers of WA, or OMRI, or IFOAM, for example. The synthetic chelated compounds that Thomas was talking about may leave not-particularly wonderful residues in the plant. At least with the organic-approved chelated minerals, the plant has enzymes and waste-removal mechanisms to deal with the chelating material once the mineral is released from the mineral within the plant.

All a chelation step does is neutralize charge, essentially, so the plant can move the mineral through the cell membrane and cell wall.
>
> I was under the impression that beneficial microbes were required to separate the chelated molecule BEFORE it actually went inside the plant.

I am not aware of this step as a BEFORE step. In fact, I don't think cleavage could happen BEFORE moving across the cell membrane. Without hte chelating agent, the material would not cross the membrane.

Microbes do much of the work of chelating mineral elements. Bacteria and fungi need chelated minerals in order to move them into their cells. So bacteria and fungi do alot of chelation of charged materials.

It's why I always have to sigh and roll my eyes heavenward when scientists talk about soil around roots of plants becoming acidified when nitrate is taken up. Only happens in sick plant root systems, otherwise there are all these healthy microbes just itching to get those "extra" hydrogen ions.....

> Apparently this is not so. Apparently, the chelated molecule goes into the plant intact.

The microbes chelate minerals before the passage through a membrane can happen. Often the microbes provide the proteins or amino acid molecules to do the process of chelation, as well as doing the work to chelate.

> What happens to the chelated molecule AFTER it goes into the plant?

The plant has enzymes that remove the protein, amino acid, or other neutralizing elements so the mineral can be put where it is needed in the cellular machinery.
 
> Can the plant utilize the chelated molecule intact?

Probably, but usually the carbon atoms and the mineral atom are needed in two different places, so there is no requirement for them to stay together.

> Are there beneficial microbes inside the plant that separate the chelated molecule (ex. into EDTA and iron) so the plant can use it?

The plant has enzymes it makes itself, inside the cells, which do the work here.

> Are there other biological processes that go on inside of the plant that break apart the chelated molecule so the plant can use it?

Yes.

> What happens to the chelation material (ETDA, lignin, etc.)
> after the plant utilizes the metal molecule?

Lignin has to be broken down through enzymatic cleavage. But lignin is a nasty compound, and the plant usualy just spits it back out. Synthetic chelators probably are just spit out as well. Amino acids and proteins are used in cellular synthesis.

OK?

Elaine Ingham
President, Soil Foodweb Inc.
SFI Corvallis, OR
SFI Port Jefferson, NY
SFI Lismore, NSW, Australia
SFI Hilversum, The Netherlands
SFI Cambridge, New Zealand
www.soilfoodweb.com

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Received on Wed May 28 2003 - 02:28:39 EDT

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