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[APD] Re: water and electrolytes

Wright wrote:

> Medical types usually define blood electrolytes as Ca++, Mg++, Na+, and K+. 
> The first two are divalent ions that contribute to hardness and the others 
> are monovalent and not involved in GH at all (i.e., don't make soap scum 
> form). All are important to transporting "stuff" across cell walls. I think 
> their ratios are often more important than absolute quantity.

In addition to those nice positively charged electrolytes plants must carry 
enough negatively charged electrolytes (anions) to balance the charges.  
Oddly, there's hardly anything on the list of essential elements that forms 
anions and those aren't found in plants at levels that are high enough to 
come anywhere near balancing the charge.

Plant analyses I've seen show concentrations of chloride -- a common anion -- 
far in excess of the plant's nominal requirement for chlorine.  I've seen 
fluids in plant cells refered to in literature as potassium chloride 
solutions.  I think it's interesting that chloride -- a constituent that some 
aquarists rumor over and many aquarists want to avoid -- may be even more 
important than it's role as a trace nutrient might imply.

I understand that plants can generate organic anions to help balance the 
charges.  But from the analyses I've seen it seems that plants will use 
chloride when they can get it.  Using chloride may save the carbon and the 
energy that the plants would otherwise expend to make organic anions.

Roger Miller
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