Main nutrient that supports old growth?

[HiNtZ]

Goes without saying that they are all important in combination, but who's the biggest player for sustaining the old growth? And who's mostly busy with the new growth?

Macro or micro, it doesn't matter..... I'm assuming it would more likely be one of the macros than trace... I don't know. Probably a stupid question, but there you have it.

 

[dw1305]

Hi all,

I'm assuming it would more likely be one of the macros than trace

Yes, plants need all the macro and micro-nutrients to sustain growth, but it different amounts. Plants are carbon based, and after that they need most nitrogen (N) and potassium (K), followed by phosphorus (P), then magnesium (Mg), iron (Fe) etc.

but who's the biggest player for sustaining the old growth? And who's mostly busy with the new growth?

It really depends on whether an element is <"mobile within the plant">. If mobile elements are in short supply the plant will move them from <"older leaves to younger leaves">, but if an element isn't mobile it can't be moved. This leads to different patterns of deficiency.

This is probably iron deficiency, you can see it effecting the new leaves, because Fe isn't mobile within the plant (from <"Help me.....">).

cheers Darrel

 

[HiNtZ]

That's very interesting that you post that picture - rotala right? Has it got some terrestrial leaves still there? Mine is way past that stage but looking like I have a similar problem.

Here's mine.



What could be causing the Fe to be immobile? Is there a relationship between Fe and magnesium somewhere? Does either one act as a catalyst for the other? Would an Fe test kit be worth it, or are they as inaccurate as the rest supposedly are? Also, sorry for bombarding you with questions - I just like to cover all bases..... would high phosphates (whether natural, or supplemented) be anything to do with this little love triangle somehow locking Fe out and not making it available in a mobile form? If so, does this happen in the plant itself, or in the water column before the plant has a chance to even see the iron?

 

[dw1305]

Hi all,

Mine is way past that stage but looking like I have a similar problem.

That is classic iron induced chlorosis.

What could be causing the Fe to be immobile?

It is just to do with plant physiology, once the Fe++(+) ion is built into proteins (like <"ferredoxin">) the plant can't break these down to re-use the same iron ion in new leaves. Mobile elements (as ions) like nitrogen, potassium, phosphorus, magnesium etc. can be moved around the plant, which means that they can be withdrawn from shaded leaves and re-deployed in new leaves.

Is there a relationship between Fe and magnesium somewhere?

Sort of, high levels of calcium ions can limit the uptake of both of them.

Would an Fe test kit be worth it, or are they as inaccurate as the rest supposedly are?

It is quite easy to measure metal ions in solution, the problem with iron is that it is pretty much universal in all soils and waters. Iron is the 4th most abundant element in the Earth's crust, but 99.9% of that iron is bound in insoluble compounds and unavailable to plants. Iron ions will become available in acidic anaerobic (reducing) conditions (and rapidly becomes toxic), but as soon as oxygen becomes available, and pH rises, the iron becomes unavailable again. Laterite is a soil composed of insoluble aluminium & iron compounds (all the other soluble elements have been removed), and none of this iron is available unless you have reducing conditions.

would high phosphates (whether natural, or supplemented) be anything to do with this little love triangle somehow locking Fe out

In alkaline conditions you get insoluble iron phosphates formed, but usually high levels of phosphorus are thought to aid iron uptake. Iron is really difficult to keep in solution in hydroponics etc where you don't have a potentially anaerobic substrate, and this is why chelators like FeEDTA are used. Iron is very tightly bound to the chelator but becomes available via photo-degradation.

If so, does this happen in the plant itself, or in the water column before the plant has a chance to even see the iron?

In solution.

cheers Darrel

 

[HiNtZ]

That is classic iron induced chlorosis.

Thank you so much for confirming this for me!

It is just to do with plant physiology, once the Fe++(+) ion is built into proteins (like <"ferredoxin">) the plant can't break these down to re-use the same iron ion in new leaves. Mobile elements (as ions) like nitrogen, potassium, phosphorus, magnesium etc. can be moved around the plant, which means that they can be withdrawn from shaded leaves and re-deployed in new leaves.

Got it - very concise explaination.

Sort of, high levels of calcium ions can limit the uptake of both of them.

Are we talking high levels of calcium in contrast to low magnesium in any hardness water, or just really very hard water with high levels of CaCo3. My water is cut with RO 50/50 which sees me around 6Gh 5Kh 7PH - magnesium is super lean in my tap so I supplement some MGSO4 to raise the GH a couple of degrees. If magnesium is missing, or in a much higher than required concentration, can that affect the uptake of Fe? Could it be said that in that sort of water calcium ions physically can't be at "high levels"?

It is quite easy to measure metal ions in solution, the problem with iron is that it is pretty much universal in all soils and waters. Iron is the 4th most abundant element in the Earth's crust, but 99.9% of that iron is bound in insoluble compounds and unavailable to plants. Iron ions will become available in acidic anaerobic (reducing) conditions (and rapidly becomes toxic), but as soon as oxygen becomes available, and pH rises, the iron becomes unavailable again. Laterite is a soil composed of insoluble aluminium & iron compounds (all the other soluble elements have been removed), and none of this iron is available unless you have reducing conditions.

By "reducing", do you mean an acid environment as opposed to alkaline - I inject CO2 which put's be down to about a 6.6pH. I understand that this is considered "acidic", is that correct? Are these the conditions you mentioned that can unlock the Fe from the insoluble compounds in the substrate? Does this include substrates such as fluorite?

In alkaline conditions you get insoluble iron phosphates formed, but usually high levels of phosphorus are thought to aid iron uptake. Iron is really difficult to keep in solution in hydroponics etc where you don't have a potentially anaerobic substrate, and this is why chelators like FeEDTA are used. Iron is very tightly bound to the chelator but becomes available via photo-degradation.

I see - so in a tank of 6.6pH the Fe binding with the phosphates isn't as bad as say a tank at 7.6pH? Is this why macro and micro aren't dosed same day? I just think that after a big water change and adding macronutrients on day 1 without having much, if any Fe on that first day will cause problems in a high tech tank. What is the solution to ensuring there is sufficient Fe and PO in the water column, available to plants on day 1 without them binding and effectively making the Fe useless?

In solution.

Awesome.


You probably really hate me right now and wish you hadn't got involved. Remind me to buy you a drink! If you want some Amanos and are local to SW London you're more than welcome, I've got loads of them.

Cheers

Spence

 

[dw1305]

Hi all,

By "reducing", do you mean an acid environment as opposed to alkaline

Sorry should have linked it in, it is the reverse of oxidation, conditions will be acidic, but "reducing" has a <"specific chemical definition">.

Reduction is the gain of electrons or a decrease in oxidation state by a molecule, atom, or ion.

Are we talking high levels of calcium in contrast to low magnesium in any hardness water, or just really very hard water with high levels of CaCo3. My water is cut with RO 50/50 which sees me around 6Gh 5Kh 7PH - magnesium is super lean in my tap so I supplement some MGSO4 to raise the GH a couple of degrees. If magnesium is missing, or in a much higher than required concentration, can that affect the uptake of Fe?

No, you should be fine. Your water won't be saturated with Ca++ ions, because CaCO3 is pretty insoluble, so there will be magnesium ions (Mg++) available to the plant.

The lack of iron ions is just a solubility issue.

Remind me to buy you a drink! If you want some Amanos and are local to SW London you're more than welcome, I've got loads of them

Very kind of you to offer, but you are fairly safe, I rarely venture south of Kew Gardens.

cheers Darrel