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>Paul Sears asked for the references Diana Walstad used for her comments on
>photoreduction of iron..... here they are:
>Re: Free iron (Fe++ and Fe+++) being the only two forms of iron used by
>- Anderson MA and Morel FMM. 1982. The influence  of aqueous iron chemistry
>on the uptake of iron by the costal diatom Thalassiosira weissflofii.
>Limnol. Oceanogr. 27:789-813.

Thalassiosira eh?Coastal algae?
Yea, I had a bad rash of that in my tank last week<G>.
Does this support the claim for FW algae in planted tanks???

>- Sunda WG, Huntsman SA, and Harvey GR. Photoreduction of manganese oxides
>in seawater and its geochemical and biological implications. Nature

>Re: UV and blue light sources inducting the most photoreduction because
>wavelengths below about 500 mn are energetic enough to break the chemical
>bonds. [the 280 - 400 nm portion of the light energy spectrum encompasses UV
>(ultraviolet) light, while the 400 - 500 nm range consists of violet and
>blue light.]
>- Morel FMM. 1983. Principles of Aquatic Chemistry. John Wiley & sons (NY),

At what intensity? Sunlight? Burns my skin too.
Some Seawater doesn't apply to FW chemistry IMO. I would not generalize that
much. Toward the longer areas(the "blue") the ability typically is less to
break these bonds is it not? It may take a few days for this to happen under
tank conditions or longer by which time most of the e iron has been used by
anyway? Assuming automatically that 7100k's are doing this is hasty, without
proof. How long does it take for 50/50 bulbs or 7100 bulbs to do this? Are
the growth rates the same in the test tanks? 7100k bulbs will not grow the
plants as fast leading to a false reading of iron compared to the 5000k lit
tank with same plants. Basically the iron is getting used up for growth in
one tank and not in the other. How much lighting is required to do this?
Thought provoking, eh? Lots of work ahead!

>Re: [rooted] aquatic plants readily take up iron from the water, even when
>planted in iron containing substrates.
>- Basiouny FM, Garrard LA and Haller WT. 1977. Absorption of iron and growth
>of Hydrilla verticillata (L.F.) Royle. Aquat. Bot. 3:349-356.

This plant is a true aquatic and is well adapted to getting iron out of the
water column. Most plants will get the water column iron as well as the soil
iron. Bacteria play a large role in both pathways IMO.
Many plants we keep are not this well adapted. Compare this to a Sword plant
and tell me what you think. Plants do both IME......... some more than
others. There are so many plants we keep and saying one plant does this or
that is difficult........... this makes it hard to generalize. I hope to
someday go through each plant in mono-culture and figure out what each plant

Are my comments incorrect?
Tom Barr