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Re: iron

> There have been discussions of this before.  As far as I know,
> plants have no problem using ferric iron.  In fact, NaFeEDTA (Fe III) is
> used as an iron supplement in agriculture.  I seem to recall Dave
> Huebert confirng this quite a while ago.

I can confirm this. The plant leaves the chelator on the out side of the
root/shoot cell and takes in the Fe via ferric reductase. This occurs on the
outer surface of root epidermal and some shoot cells.
There is a two step process to this uptake whereby a transportor then takes
in the reduced Fe2+.

Then most plants use their own internal chelator to transport the iron.
So there are two cell surface enzymes doing the work. Cu plays a large role
in the uptake of Fe also.
The roots also add H+ to acidify the root zone and help increase the
solubility of the iron.

One interesting part of this are the organic ligands role. These occur from
regular decomposition of detritus and this is mediated by bacteria and
fungi. These greatly increase bio available occurring Fe levels by
10-100,000X by acting like a chelator.

I feel that the bacterial/fungal cycling of this detritus plays a large role
in a mature tank with good O2 levels(since both of these groups are
dependant on O2) within the substrate.

The levels of these chelator (artificial or otherwise) increase near the
roots since the roots do not use them as they remove the Fe from the
chelator. So many of these chelators are available to bind Fe again.

Most all plants use this above process except for members of grass family.
Tom Barr

> Paul Sears