Abstract: The changes of the nucleolus during cell cycle in Triticum aestivum were studied by Bernhard staining method. It was observed that in interphase, the nucleolus was heavily stained. Fibrillar centers, dense fibrillar component, granular component could be identified in it. But the chromatin was bleached. The fine RNP granules were distributed at the interchromatin. During prophase, the small RNP granules appeared at the periphery of chromosomes. The larger heavily-stained RNP granules accumulated at the periphery of the metaphase chromosomes and formed a discontinuous "sheath"-like structure. They were not observed at the interior of the chromosomes. This "sheath"-like structure was also observed at anaphase. In telophase, the nucleolar materials were progressively separated from the "sheath" and participated in the formation of new nucleoli. The results showed that the nucleolar materials were transferred directly to the surface of the metaphase chromosomes and formed a discontinuous coat, but not incorporated into the interior of the chromosomes.

Key words: perichromosomal RNP, nucleolar RNP, triticum aestivum