Iron and red plants

[paludarium]

OK, I know anthocyanin does not contain iron or any other metal. However, many folks DID report that the plants truning red after adding more iron to the water column. I would like to find out why hobbyists keep reporting that iron makes the plant red.

Correct me if I am worong. Excessive Fe uptake results in increased polyphenol oxidase activity, leading to the production of oxidized polyphenols, the cause of leaf bronzing. Large amounts of Fe in plants can give rise to the formation of oxygen radicals, which are highly phytotoxic and responsible for protein degradation and peroxidation of membrane lipids.

Anthocyanins appear to protect plants from permanent damage by acting as antioxidants. However, if the concentration of free radicals exceeds the ability of natural of natural antioxidants to quench them, iron toxicity may ensue.

Too much iron caused leaf bronzing (red?), and before the iron toxicity really develops, anthocyanins, which turn the leaves red, act as antioxidants to protect the plants. I am not sure of this, but might it be a sign of iron toxicity if we add too much iron consequently the plants turn red?

 

[Tom Barr]

Re: Iron and red plants

OK, I know anthocyanin does not contain iron or any other metal. However, many folks DID report that the plants truning red after adding more iron to the water column. I would like to find out why hobbyists keep reporting that iron makes the plant red.

Well, you might also ask them why they assume excess nutrients cause algae, say PO4 at 2-3ppm. Just because they say so, does in no why imply they or any myth is correct. The issue with Fe is much more general. It affects many things, not just "red coloration". That is a marketed reason to buy Fe/trace additions, not a scientific one. Overall health is a much better idea/concept. This does lead to better coloration overall, better health etc... not just more red.

Correct me if I am worong. Excessive Fe uptake results in increased polyphenol oxidase activity, leading to the production of oxidized polyphenols, the cause of leaf bronzing. Large amounts of Fe in plants can give rise to the formation of oxygen radicals, which are highly phytotoxic and responsible for protein degradation and peroxidation of membrane lipids.

Yep.

Anthocyanins appear to protect plants from permanent damage by acting as antioxidants. However, if the concentration of free radicals exceeds the ability of natural of natural antioxidants to quench them, iron toxicity may ensue.

Key word is "appear". Antiherbivory is another thing they "appear" to do, or UV protection is yet another function that they "appear" to do.
The other thing is, at least in our tank's etc, other trace elements are key to production of antioxidants. You'll see this in the next Issue.

Since Fe is the only thing often tested, many of the other metals are often ignored as well as their role, function.

The plant general can regulate the amounts of Fe at the levels we add, toxicity has never been observed to date in a planted tank due to excess Fe.
I've tried.

I added 200mls in an 75 liter tank of Flourish to give you an idea and waited several days. No one is going to add even 10x less that amount. 20mls 3x a week is a bit excess on such a tank(even EI, which is fairly rich by most standards suggested 5mls 3x a week or so), yet no ill effects, no reddening etc was observed, no shrimp deaths etc. I've added 15mls x 3 weekly of TMG in the past without issues.

You tend to get better brozing with TMG, and nice sheen would be a better description. This does appear to be a negative look and is mainly in Crypts.

Too much iron caused leaf bronzing (red?), and before the iron toxicity really develops, anthocyanins, which turn the leaves red, act as antioxidants to protect the plants. I am not sure of this, but might it be a sign of iron toxicity if we add too much iron consequently the plants turn red?

You are certainly on a much better, and more supportable path here than the other arguements which suggest Fe helps plants to produce reds. Rather, a toxic effect produces the reds.

I see very red plants that often are not very red, and I think a stressed plant.
But generally the red coloration can be brought out much better with low NO3 and higher GH's.

The brozing is notable at high dosing levels, but looks nicer, it mightn be due to the excess Fe, but it would seem we are a long way from that level with our plants as adding more and more Fe slowly and progressive would cause a breakdown and overload that would reduce growth, cause cell lysis etc.
But we do not observe that as we add more and more Fe.

At least I never have and I have added and played with high Fe levels/traces for many years. But adding just Fe, rather than and general trace mix would answer this question relative easily.

Start at a high rate for us(say 10mls /75 liters daily), then keep increasing the mls/adding it till you see some negative responses.
You do not even need a test kit to do this test.

You need to wait about 1-2 weeks between increases to see a plant response.

I honestly do not know if you can roast the plants with high Fe internally like this(external is another matter) and force pigment changes. If the plant has no other choice for various trace metals but to take in Fe along with the Cu, Zn etc, and lives rooted in a very high Fe levels soils etc.......maybe.

But on a more practical level, a simple test to see if the plant will respond negatively would add support for this idea. I just question at what level is the excess Fe going to cause the coloration and is it due to this mechanism.




Regards,
Tom Barr

 

[paludarium]

Re: Iron and red plants

Thanks for the reply.

Diana Walstad quoted a few studies as evidences of iron toxicity in her book " Ecology of the planted aquarium". I am not sure whether those cited studies were carried out in the tanks. Soil matter might play an important role here, right?

You have already repeatedly elucidated that the red coloration can be brought out much better with low NO3. But now with higher GH's, well, I love to learn more about that.

 

[Tom Barr]

Re: Iron and red plants

I'm not excatly sure why the higher GH's appear to do this, just something I've noted as well as a few others.

DW reports that because there are cases in wetlands of this occuring, but whether that can applied here remains an entirely different matter.
She tried this with laterite and soil, that's a bad comboniation..........but she says she assumed it was Fe, but it could have been Al3+ toxicty as well.
Did she trest for that? I dount it. That's very common as well and laterite has that also. Point is, it does not rule out many other potential issues.
56ppm of Fe in the pore water is pretty high.

We are VERY long water from that, and we also do more water changes, use less organic matter thus have less issues with reduction and release of metals in the substrate, what occurs in the substrate is quite different from what occurs in the water column, they are often very poorly correlated.

ZnCu SOD enzymes are the antioxidants that quench O2 radicals.

So enough of these can help allivate oxidant stresses, as will good levels of Mg, Mn etc.

I've still never noted much corrleation between intense reds in excessive Fe dosings. Some claim so. That all well and fine, but the effects are subtle at best.

It seems to be much more an overall health approach with adequate Ca/Mg/SO4, Traces etc, rather than toxic effect of Fe.

But if you have a bottle of Fe from Flourish Iron from SeaChem, why not try it out and see if the prediction holds true?

That adds only Fe.

Recall, we added and still do in many locations, laterite at high levels.
Reduction occurs in many soils etc, this means lots of Fe.

It really don't see much of this occuring(fe toxic = reds).
I could certainly be wrong, but I would not argue for it either.

On anothwer note,s while I may disagree with a quitre a few things in her book, she does qualitfy herself well and makes clear when she suggest something and what reference it's from. She has a lot of verty right things folks seem to overlook. I'm not sure why.

Figures on page 130-131, pages 124, 127, are all good.
Table on 128 on the other hand has errors, NO3 reduction does not ioccur at 421 mv, nor Mn reduction in a substrate, nor does Fe reduction occur at such a low level.

Interptations are another matter, the reader is often left assuming what is implied. That is not her fault.

Still, she did do a wonderful job and the references are a first for planted tanks in any book.

Regards,
Tom Barr



Regards,
Tom Barr