The Ultrastructure and Analytical Microscopy of Silicon Deposition in the Aleurone Layer of the Caryopsis of Setaria italica (L.) Beauv.

Silicon deposition in the caryopsis of foxtail millet (Setaria italica (L.) Beauv.) from Lin Xian, Northern China was investigated using transmission electron microscopy and energy dispersive X-ray analysis. The highest silicon count rates were obtained from the pericarp and outer aleurone cell walls, and particularly from a granular electron-opaque layer external to the outer aleurone cell wall. Silicon was not detected in tissues interior to the aleurone. A possible mechanism for silicon deposition in the caryopsis is suggested, and the results are discussed with respect to the high incidence of oesophageal cancer in Lin Xian, Northern China.