Silicon, oxygen and carbon isotope composition of wheat (Triticum aestivum L.) phytoliths: implications for palaeoecology and archaeology

Abstract

2008. Silicon, oxygen and carbon isotope composition of wheat (Triticum aestivum L.) phytoliths: implications for palaeoecology and archaeology.ABSTRACT: Six mature wheat (Triticum aestivum L.) plants from one crop were collected one week before harvest, and organs were separated as follows: culm, rachis, leaf sheaths, leaf blades and inflorescence bracts. Percentage silica (% SiO 2 ), % C, % N and d 13 C were determined in these samples. Phytoliths isolated from the individual organs were subsequently analysed for d 29 Si, d 30 Si, and d 18 O, as well as % C, % N and d 13 C from occluded organic material within the phytoliths. Percentage silica was highest in the leaf sheaths and leaf blades and lower in the inflorescence bracts, culm and rachis. d 30 Si and d 29 Si were highly correlated, and both increased in the upper parts of the plant. It appears there are two routes for Si transport within the plant, and that heavier isotopes increase towards the end of both routes. The d 18 O results indicate that the culm and the leaf blades were the sites of highest d 18 O, with lower values in the rachis, leaf sheath and inflorescence. There was no correlation between the accumulation of either heavy silicon isotope ( 29 Si and 30 Si) and heavy oxygen accumulation ( 18 O). d 13 C values were typical of C3 species, and whole plant and isolated phytolith values were similar. Low % N concentrations were detected in phytoliths. # Natural Environment Research Council (NERC)

A Review of the Stable Isotope Bio-geochemistry of the Global Silicon Cycle and Its Associated Trace Elements

“…Beyond this, there is clear evidence that significant isotopic fractionation can occur between plants with increased fractionation in heavy Si accumulators (Ding et al, 2005(Ding et al, , 2008aOpfergelt et al, 2006a,b). Rayleigh fractionation during the transportation of Si within plants also causes heavier isotopes to be concentrated within the xylem whilst lighter isotopes are preferentially deposited in phytoliths lower down the plant (Ding et al, 2005(Ding et al, , 2008aOpfergelt et al, 2006a,b;Hodson et al, 2008). Phytoliths have higher dissolution rates than other silicate materials (e.g., tephra, clay, feldspars, quartz), and provide a major source of DSi in some soil/terrestrial environments (Derry et al, 2005;Struyf et al, 2009;Cornelis et al, 2010;Opfergelt et al, 2010).…”

A review of diatom δ18O in palaeoceanography

“…Furthermore while the use of heavy liquids, such as SPT, often enable the separation of diatoms from non-diatom material, in many cases the similar densities between diatoms and clays/silicates can prevent complete separation (ibid). This problem may be exacerbated in the marine environment by the presence of other siliceous organisms such as radiolarians, sponges or phytoliths, the δ 18 O of which remains poorly understood (Mopper and Garlick, 1971;Matheney and Knauth, 1989;Webb and Longstaffe, 2003;Hodson et al, 2008).…”

Application of Fourier Transform Infrared Spectroscopy (FTIR) for assessing biogenic silica sample purity in geochemical analyses and palaeoenvironmental research

“…Increased attention is focused on the potential for geochemical measurements of biogenic silica to be used in palaeoenvironmental research in both continental, riverine, lacustrine and marine settings (e.g., Filippelli et al, 2000;de la Rocha et al, 2000;de la Rocha, 2003de la Rocha, , 2006Derry et al, 2005;Hendry and Rickaby, 2008;Hodson et al, 2008;Opfergelt et al, 2008;Swann et al, 2010). These studies, most commonly involving the analysis of diatoms, plant phytoliths, radiolaria and siliceous sponges, are believed to be particularly important in attempts to better understand the global silicon cycle as well as high latitude environmental change in regions where carbonates are not readily preserved in the sediment record (Conley, 2002;Street-Perrott and Barker, 2008;Leng et al, 2009;Swann and Leng, 2009).…”