Stability and Variability of Chromosome Numbers in the Genus Schoenoplectus (Cyperaceae). I. S. gemmifer, S. mucronatus var. mucronatus and S. triangulatus

The chromosomes of the new species Schoenoplectus gemmifer and the allied S. mucronatus var. mucronatus and S. triangulatus were studied in culm-apex cells and root-tip cells. The mitotic metaphase chromosomes were small and dot-like. The chromosome number in culm-apex cells was stable and was observed to be 2n=74 in S. gemmifer, 2n=38 in S. mucronatus, and 2n=42 in S. triangulatus, respectively. Thus, it was confirmed that the new species S. gemmifer was cytologically different from both S. mucronatus and S. triangulatus. Inter- and intra-individual variations in chromosome number, mixoploidy and aneuploidy, were found in the root-tip cells of the three species. Chromosome number (2n) varied from 68 to 74 in S. gemmifer, 2n=32 to 39 in S. mucronatus and 2n=37 to 44 in S. triangulatus, respectively. This phenomenon is very rare and this is the first report in the genus Schoenoplectus.