Silica Distribution in the Caryopsis and Inflorescence Bracts of Foxtail Millet [Setaria italica (L.) Beauv.] and its Possible Significance in Carcinogenesis

Silicon deposits in the caryopsis and inflorescence bracts offoxtail millet Setaria italica (L.) Beauv.] were investigatedusing light microscopy, scanning electron microscopy and electronprobe microanalysis. The samples were obtained from Lin Xian,Henan province, northern China and CSIRO, Australia. High concentrations of silicon were observed in the papillaeon the external surfaces of the inflorescence bracts, and inthe epidermal cells. In the caryopsis silicon was depositedin the aleurone layer. Silicification was heavier in the LinXian samples. The heavy accumulation of silica in the foxtail millet and thepossibility that fragments of plant silica may be implicatedin the aetiology of oesophageal cancer in the Lin Xian regionare discussed. Setaria italica (L.), Beauv, foxtail millet, caryopsis, silica distribution, scanning electron microscopy