Mysterious issue with multiple plants

[dw1305]

Hi all,

In nature, there's usually no scarcity of Ca and Mg, but only few K. On the other hand, plants (dicotyledons) require K >> Ca > Mg. Thus, plants take up K preferentially. If you overdose K you create an unnatural environment and many species cannot handle it.

There is a paper <"Regulation of K+ Nutrition in Plants">, that talks about potassium (K+) uptake, transport and storage.

Not surprisingly, plants have evolved a large ensemble of K+ transporters with defined functions in nutrient uptake by roots, storage in vacuoles, and ion translocation between tissues and organs. This review describes critical transport proteins governing K+ nutrition, their regulation, and coordinated activity, and summarizes our current understanding of signaling pathways activated by K+ starvation

............ At low K+ concentration, active transporter systems are needed in order to pull K+ inside the cell against its electrochemical gradient. However, studies in several plant species have shown that channels may be involved in K+ uptake in the high-affinity range of K+ concentrations.............

According to my observations, serious problems are widespread if there's more K than Mg in the water.

I'm guessing that is actually most of us. We don't have much magnesium (Mg) in our tap water (<"for geological reasons">) and I'd expect that most people add less Mg than they do K.

I'l admit I'm still slightly dubious, just <"because horticultural fertilisers"> add more potassium (K) than magnesium (Mg) and they have to "work".

I don't know in my case, I practice <"very lean dosing"> (but not in a <"very analytical manner">) and I add a <"small amount of extra magnesium (Mg)">, mainly on grounds of <"if it ain't broke, don't fix it.">

*Ragel P, Raddatz N, Leidi EO, Quintero FJ, Pardo JM. Regulation of K+ Nutrition in Plants. (2019) Front Plant Sci. 10:281.

cheers Darrel

 

[MichaelJ]

Beware, the ratios are molar. Translated into weight ratios it returns K : Mg : Ca = 1 : (no less than) 3.1 : (no less than) 10.2.
Like I said in another post, you can handle Mg : Ca ratio rather freely. Overdosing potassium is much more dangerous. But even in the case of potassium, you don't have to take my ratio too rigidly.
I think the essential fact is this: In nature, there's usually no scarcity of Ca and Mg, but only few K.

When looking at natural waterways in the Amazon (below) its clear that the Mg:Ca ratio can vary quite a bit (if you disregard the outliers there is a trend around 3-4:1 however). but it seems that the amount of K is usually higher than the amount of Mg, but all in very small amounts so that may play a role as well.

On the other hand, plants (dicotyledons) require K >> Ca > Mg. Thus, plants take up K preferentially. If you overdose K you create an unnatural environment and many species cannot handle it.
According to my observations, serious problems are widespread if there's more K than Mg in the water.

I think many (or most) of us run our tanks at higher K than Mg levels and most of us are able to keep our plants healthy despite of that. I am wondering what role absolute quantities plays relative to the ratio here. Perhaps there is a grey area where the ratios matters less than the absolute quantities or perhaps interactions with other tank parameters plays into this as well.

Anyway, I think this is all really fascinating stuff and I encourage you to keep up the good work @_Maq_ ! Hardly any of us in the community have the skills, time and dedication to run such experiments.

Cheers,
Michael