Abstract
Actively growing root tips of Vida fabaexcised to about 5 mm length were exposed to hypoxia and the structures of nucleoli were examined under light microscopy. Hypoxic conditions were attained by boiling distilled water for 10 min and immediately cooling with cold tap water. The excised root tips were placed in this hypoxic water for 1, 2, 4, 8, and 16 hr. Controls were kept in distilled water with continuous aeration for the same times. A structural alterations first discerned at 1st hr under hypoxia was segregation of the nucleolar components. This phenomenon, so called the nucleolar segregation, was prominent until 4th hr. Then, the nucleoli began to erode extremely through dispersion, projection or fragmentation of the nucleolar material after the nucleolar segregation. The nucleolar erosion continued to exposed argyrophilic strands, which consisted of beaded segments. These strands are expected to correspond with the nucleolar organizing secondary-constrictions.
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