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

Abstract

AbstractSix 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 (% SiO2), % C, % N and δ13C were determined in these samples. Phytoliths isolated from the individual organs were subsequently analysed for δ29Si, δ30Si, and δ18O, as well as % C, % N and δ13C 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. δ30Si and δ29Si 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 δ18O results indicate that the culm and the leaf blades were the sites of highest δ18O, with lower values in the rachis, leaf sheath and inflorescence. There was no correlation between the accumulation of either heavy silicon isotope (29Si and 30Si) and heavy oxygen accumulation (18O). δ13C 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) copyright 2008. Reproduced with the permission of NERC. Published by John Wiley & Sons, Ltd.