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Re: CEC
Roger Miller wrote:
> According to the "classic" model for cation exchange, positively
charged
> ions are bound to negatively charged particles in the substrate or
soil.
> The binding sites are pretty much always occupied by something (if
not,
> then the soil or substrate will take on a net negative charge); to add
> something new to a binding site it has to be exchanged for something
> that's already bound there (hence the "exchange" in "cation exchange
> capacity"). This is a completely reversible reaction.
>
> Removing an ion without exchanging it for something else would take
some
> work (this involves exponential functions with upper case chi's and
curly
> F's and it's really way too messy for me to think about). I think
plants
> get around that by transporting positively charged ions out through
their
> roots and trading them for the ions that are on the exchanger. There's
> some sort of work involved in that, too. But its easier to think
about.
>
Maybe I'm showing my ignorance here, but does anyone know
exactly what the plant is trading off in this process?
Eric Deese
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