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

Abstract

Silicon deposits in the caryopsis and inflorescence bracts of foxtail millet [Setaria italica (L.) Beauv.] were investigated using light microscopy, scanning electron microscopy and electron probe microanalysis. The samples were obtained from Lin Xian, Henan province, northern China and CSIRO, Australia. High concentrations of silicon were observed in the papillae on the external surfaces of the inflorescence bracts, and in the epidermal cells. In the caryopsis silicon was deposited in the aleurone layer. Silicification was heavier in the Lin Xian samples. The heavy accumulation of silica in the foxtail millet and the possibility that fragments of plant silica may be implicated in the aetiology of oesophageal cancer in the Lin Xian region are discussed.