"John Ronald Reuel Tolkien, author of The Hobbit and The Lord of the Rings, was born on this site on 3 January 1892," reads an iron plaque engraved in English and Afrikaans.
Iron oxidizing bacteria may enhance the formation of more iron plaque.
Most of the aquatic macrophytes possess iron plaque around the roots and submerged parts (King and Garey 1999) and sequester metal ions from water (Hansel et al. 2001).
Although this process enhanced the formation of Fe-enriched coatings on root surface, it appears that root plaque had limited effects on inhibiting As uptake since most of the young roots were not covered by iron plaque.
Many wetland species exhibiting radial oxygen loss show the unique feature of iron plaque being deposited on mature parts of their roots (St Cyr and Crowder 1988) reducing the chances of toxic metal absorption through diffusion (Greipsson 1994).
Iron plaque is layer of iron (hydr)/oxide precipitate around the plant parts caused by oxidation of iron by molecular O2 or by iron oxidizing bacteria (e.g., Ferroplasma sp. and Leptospirillum ferroxidans) (King and Garey 1999).
