CHANGES IN CHROMOSOMAL ULTRASTRUCTURE DURING THE CELL-CYCLE

The surface structure of mitotic barley and rye chromosomes was studie d by high-resolution scanning electron microscopy. Chromosomes with va rious degrees of chromatin condensation were prepared from untreated m eristematic tissue of root tips. At lower magnifications the highly co ndensed chromosomes in metaphase and anaphase showed a compact structu re with a smooth surface. The condensation starts from the centromeric region and the chromatids are often discernible in the still unconden sed telomeric region. Decondensation begins at the telomeric region du ring telophase. Parallel arrangement of fibres is a characteristic fea ture predominately seen in prophase and telophase chromosomes. Chromat in structures that resemble tiles on a roof or braided strands were of ten observed. Prophase and telophase chromosomes are particularly suit able for further studies of chromatin arrangement and organization in plant chromosomes.