The fine structure of the cells that perceive gravity in the root tip of maize.

Within the root cap, in maize, the cells believed to be responsible for the perception all possess large well-developed amyloplasts. They also have normal mitochondria and Golgi bodies, normal rough-surfaced ER with a very striking pattern of distribution, few free ribosomes, walls with an abnormal reticulate encrusting material, irregularly distributed plasmodesmata and an as yet unidentified fine quadruple membranous system. All of these features are discussed in relation to the role of the cells in perception.