ABSTRACT
7-Methoxy-, 7-methyl- and 6-methylcoumarins retarded mitosis in Allium cepa root promeristem and caused chromosomal aberrations. Chromosomes became shorter and thicker, and often were lost during anaphase, forming micronuclei during interphase. Chromatid bridges were observed in anaphase and telophase, leading to the formation of a restitutional nucleus, often of irregular shape. Abnormal fragmopasts, often discontinuous, prevented normal cytokinesis. There was increased vacuolization and the mitochondria contained an electron-dense matrix. Parts of the cytoplasm, which were surrounded by ER cisternae, contained mitochondria and pieces of ER membrane. Autophagous vacuoles showed a lower density of cytoplasm, but still contained numerous pieces of ER cisternae.
