Re: [APD] Fe and red plants

[Thomas Barr <tcbiii at yahoo_com>]

>I thought it might be a good idea because the poster didn't specify what 
>the other plants were, and since the light and CO2 were good, 
>that leaves open the possibility that the discolored plants are the 
>faster growing plants. Any deficiency would show up in the faster 
>growing plants first.
> Iron is an immobile nutrient which makes 
>deficiencies show up in the new growth first (i.e., the tops, as the poster 
>reported).
>Jerry Baker
 
Your intent is admirable.  
 
So have you seen Fe deificency in a red plant before? Not what the prevailing anecdotal advice suggest nor what is mentioned for agricultural crops living in terrestrial systems(The plant has to move the Fe to the tip from the soil, but an aquatic plant has no such issues since it it sbathed in the solution of water, unless there is not ample Fe in the water column).
 
Many folks repeat these things and I question their utility and whether they are true or not. I've tried to isolate and produce an Fe deficency with some high degree of certainly, it is rather difficult.
 
I have some pretty red plants and have found out more or less what causes color changes in red plants some years ago. I've not found those same reasons to be invalid since. A number of folks worked on that issue and then numerous folks confirmed it ever since(See here on the APD archives).
 
I've not noted any reddening or less red color from less traces.
Tips or not.  I have noticed an overall color improvement is some species and a sheen, general vitality etc in the rest of the species. 
 
An Fe level or test kit will not tell you much either(see APd archives for more on that in the past). The issue with Fe test kits has been covered a number of times, basically a residual level will not tell you what you need to know and the level moves rapidly.
There is a simple way around this issue though.
 
The other issue/myth was many folks assume that red plants need more iron than green plants.
 
Plants can and do move Fe around, they use their internal chelator to do so. EDTA, Gluconate, DTPH etc are always excluded and left on the outside of the plant when uptake occurs.
 
Do we test for Mn, Cu, Zn, B and other things in traces besides Fe?
A few might test for Cu, but I've yet to hear of anyone testing for the others............so there are a few unknowns there and many plant species behave differently to different decificencies.
 
It is therefore very difficult to use a chart of deficenies based on agricultural terrestrial systems to generalize in aquatic plants. I manipulate nutrients to extremes and have for quite a few years specifically with aquatic plants and quite a few of them(250 species? maybe more), I have not found those generalizations to true. I know your intent is good, but I doubt you'll find  much use even if they gave you accurate information on Fe levels.
 
Regards, 
Tom Barr

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