Heteromorphic appearance of acrocentric nucleolus organizer regions in Nothoscordum fragrans.

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Abstract
The nucleolus organizer regions were studied in N. fragrans, Liliaceae (2n = 19), applying the technique of C-banding. This technique distinguished 6 acrocentric chromosomes into 4 types by the banding patterns in the long arms and showed the nucleolus organizer regions and nucleoli. The distal ends of the short arms of all 6 acrocentric chromosomes had a characteristic appearance at metaphase: completely condensing, fluff-like diffusing or amorphous loosening of the chromatin. These 3 characteristic formations seemed to represent a progressive alteration of the morphology of the short arms during metaphase. These regions were confirmed to be the nucleolus organizer regions since they were attached to the nucleoli at prophase. The frequencies of the 3 characteristic formations were studied for each type chromosome. There was a quantitative difference in the diffused or loose chromatin for each type of chromosome. The possibility that this may reflect the size of the nucleolus organizer regions is discussed.