CELL WALL FORMATION IN PEDIASTRUM BIRADIATUM AS REVEALED BY THE ELECTRON MICROSCOPE

Moner, J. G. (U. Massachusetts, Amherst), and G. B. Chapman. Cell wall formation in Pediastrum biradiatum as revealed by the electron microscope. Amer. Jour. Bot. 50(10): 992–998. Illus. 1963.-An electron microscopic study of cell wall development in P. birudiatum is described. Micrographs were taken of thin sections of cells from several stages involved in the transformation of the motile zoospore into the 4-pronged adult cell type during asexual reproduction. The cell wall begins as a thin membrane which does not change noticeably during the transformation of the zoospore to the adult cell type. In a subsequent period of not more than 6 hr, a definitive cell wall arises accompanied or followed shortly by the appearance of a globular network on the underside of the cell wall proper. During all of the developmental stages osmiophilic globuli are found in the cytoplasm, frequently at the cell surface. Similar, though smaller, globuli are found in the chloroplasts of Pediastrum and other plants, indicating that these bodies may have a plastid origin. It is suggested that whole osmiophilic globuli, or parts thereof, may be transferred to the cell wall proper, giving rise, ultimately, to the globular network.