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Re: Iron, chelates, and pathways

> What is the foliar mechanism for obtaining bioavailable Fe++ ? ( how
> do  algae, rootless plants and the stems and leaves of rooted plants )  get
> bioavailable Fe++ ?

Actually its the same process as in the rhizosphere (root zone).

1. Fe+3 organic complex is reduced by plasma membrane ferric reductase
to Fe+2
2. Fe+2 is transmitted through the Fe+2 channel into the leaf or root
3. The chelator is released.

I quote from the website (reference given earlier):

"Strategy 1 - Dicotyledonous Plants 

This uses the plasma membrane H+ pump (see previous lecture) to acidify
the rhizosphere so that Fe becomes more soluble. This allows Fe-organic
complexes to form in the soil solution as the pH drops (Most Fe-organic
complexes are only stable below pH 6.0). The Fe-organic complexes then
diffuse to the root surface where they are reduced by the plasma
membrane ferric reductase to Fe2+. Fe2+ is then taken into the root cell
by a Fe2+ channel. The chelator is released and can return to the soil
where it can acts as a shuttle many times (see picture below). The root
can also produce its own chelators (e.g. the phenolic compound caffeic
acid or the organic acid citric acid). "

Steve Pushak                              Vancouver, BC, CANADA 

Visit "Steve's Aquatic Page"      http://home.infinet.net/teban/
 for LOTS of pics, tips and links for aquatic gardening!!!