Hi all,
I've been dosing additional DTPA 7% chelated iron for a while with no success and from further research realised that a lack of Mg was the real culprit since apparently its lack prevents a proper uptake of iron? So I've started dosing epsom salts since recently and things appear to be improving
Yes, it is the high levels of calcium (Ca++) ions that interferes with the uptake of magnesium (Mg++) and iron (Fe+++) ions. Because both magnesium and iron are required for the synthesis of chlorophyll, the lack of either leads to chlorosis.
Iron is a bit different to the macro-nutrients, it is similar to the other micro-nutrients (like zinc (Zn), copper (Cu), boron (B) ) in that it is essential for plant growth, but at the same time, iron is highly reactive and toxic via the <"
Fenton reaction">. This means that plants have to control iron uptake, and react to both iron deficiency and iron excess.
If you have a plant like Hornwort (
Ceratophyllum demersum), or
Vallisneria spp., they come from alkaline, high calcium environments where iron is always in short supply. They are very efficient at sequestering iron, they aren't going to show deficiency symptoms unless there really are no iron ions in solution or in the rhizosphere. Against that they may struggle in soft water, where iron toxicity could be an issue.
If you have a plant that naturally grows in acidic, very soft, water (<"
Tonina"> etc.) it will have mechanisms that efficiently exclude iron, because it is always plant available and toxicity is much more of a potential issue, <"
Rotala rotundifolia"> looks like another plant which is quick to show iron deficiency symptoms.These may relate to the dKH and pH more than the actual amounts of divalent cations (dGH).
Most plants will be somewhere in the middle, and capable of growing along in a wide range of water types.
cheers Darrel
