It is me back about Iron utilisation again. I have found, via a current
contents search, an article on Iron utilisation in terestrial plants.
Aparently grapevines, in response to Fe limitation, acidify the external
surface of the root and also increase the activity of FeIII reductase.
This would increase the solubility of the oxohydroxides of Iron found in
the soil and also allow the plant to use the FeIII much more easily. I
imagine that the same sort of system would work in aquatic plants, at
least this would suggest that plants are able to use the FeIII ion as
well as the FeII. The FeII may be used preferentially, but it still seems
that they are able to use FeIII.
The reference is
Brancodoro et al
Plant and soil 1995 vol 171(2) pp229-234.
" Mechanisms of Fe deficiency in roots of vitis spp. in response to iron