%0 Journal Article
%T New insight into silica deposition in horsetail (Equisetum arvense)
%A Chinnoi Law
%A Christopher Exley
%J BMC Plant Biology
%D 2011
%I BioMed Central
%R 10.1186/1471-2229-11-112
%X Silica deposits were observed in all plant regions from the rhizome through to the stem, leaf and spores. Numerous structures were silicified including cell walls, cell plates, plasmodesmata, and guard cells and stomata at varying stages of differentiation. All of the major sites of silica deposition in horsetail mimicked sites and structures where the hemicellulose, callose is known to be found and these serendipitous observations of the coincidence of silica and callose raised the possibility that callose might be templating silica deposition in horsetail. Hydroponic culture of horsetail in the absence of silicic acid resulted in normal healthy plants which, following acid digestion, showed no deposition of silica anywhere in their tissues. To test the hypothesis that callose might be templating silica deposition in horsetail commercially available callose was mixed with undersaturated and saturated solutions of silicic acid and the formation of silica was demonstrated by fluorimetry and fluorescence microscopy.The initiation of silica formation by callose is the first example whereby any biomolecule has been shown to induce, as compared to catalyse, the formation of silica in an undersaturated solution of silicic acid. This novel discovery allowed us to speculate that callose and its associated biochemical machinery could be a missing link in our understanding of biosilicification.Silicon is the second most abundant element of the Earth's crust after oxygen and, perhaps surprisingly, its essentiality in biota remains equivocal [1]. The difficulty in ascribing true biochemical essentiality to silicon probably emanates from a lack of demonstration of any silicon-requiring biochemistry and specifically Si-C, Si-O-C, Si-N, et c. bonds in any form of extant life [2]. However, in spite of such limitations the essentiality of silicon in plants remains the subject of rigorous debate [3,4] as do elaborations of the underlying mechanisms. Biosilicification was recently def
%K Biosilicification
%K biogenic silica
%K silicic acid
%K horsetails
%K callose
%K PDMPO
%K fluorescence
%K acid digestion.
%U http://www.biomedcentral.com/1471-2229/11/112