Department of Botany, University of Nigeria, Nsukka, Nigeria
*Forms part I of “Cytotaxonomic Survey of Some Tropical Ornamentals.”
Chromosome counts from root tip cells showed 2n=33 for Hippeastrum equestre. This species therefore, is a natural aneuploid. The odd chromosome is not considered to be a B-chromosome. Its length differed from any of the other 16 homologues and its origin is not yet unravelled. Examination of PMC showed the presence of laggards and bridges at both AI and AII, typical of inversion material. Many PMGs produced more than 4 cells at the tetrad stage and this was reflected in the very low percentage (23%) of viable pollen grains. It would seem that Hippeastrum has not arisen by simple doubling of chromosome but additionally by some internal chromosome rearrangements like inversion. These factors have resulted in complete infertility and necessitated reproduction purely by vegetative means.
