Journal of Cell Science, Vol 13, 799-809, Copyright © 1973 by Company of Biologists

Submitted on December 20, 1972

Ultrastructural Changes in Euglena After Ultraviolet Irradiation

¹ Biology Department, University of California, Santa Barbara, California 93106, U.S.A.; Smithsonian Institution, Radiation Biology Laboratory, 12441 parklawn Drive, Rockville, Maryland 20852, U.S.A.
² Biology Department, University of California, Santa Barbara, California 93106, U.S.A.

The structural changes associated with the ultraviolet-induced bleaching of light-grown cells of Euglena gracilis were investigated. Our light- and electron-microscopic observations of the bleaching process indicate that there is a continuity of plastid structure in cells 5 generations after receiving a bleaching dose of ultraviolet light. There seems to be a continuous dilution of the plastid thylakoids and a decrease in plastid size in the bleaching cells. There also seems to be a change in the position of the plastids in relation to the mitochondria in the bleaching cells. The plastids and possibly the mitochondria are the only organelles which are affected by the ultraviolet irradiation. The continuity of plastids in bleaching cells of Euglena is discussed in relation to the proposed effect of the ultraviolet light.