Studies on Centromere, Chromomere and Nucleolus in Pachytene Nuclei of Rice, Oryza sativa, Microsporocytes

Abstract

Pachytene nuclei of rice microsporocytes were examined about centromere constitution, chromomere pattern and nucleolar situation by flame drying method and Giemsa stain. Uridine treatment of intact microsporocytes before preparation distinctly revealed the centromere on late pachytene chromosomes, that is, four equal entities were detected in a centromeric region.
Chromosomes treated in KCl solusion were stained clear enough to be analysed their chromomere patterns on 12 bivalents. Mid-pachytene chromosomes were suitable for chromomere analysis and capable of discriminating 12 bivalents with their chromomere patterns, centromere position and length.
Supernumerary micronucleoli were frequently observed in a pachytene nucleus besides a macronucleolus. They were situated in three conditions; free from chromosomes, adhered to the surface of various intervening sites of chromosomes and adhered to the ends of chromosomes. In some nuclei micronucleoli appeared to be excised out from macronucleoli were noticed. These observation indicated the origin of micronucleoli.