Cytogenetic Evaluation of Microsporocytes of Setcreasea purpurea Boom Flower

Setcreasea purpurea Boom (Wandering Jews) belongs to the family Commelinaceae of order commelinales. The family, made of 38 genera and about 600 species, occurs mostly in the tropical and warm regions of the world. Many are popular as garden or house ornamentals. It is a flower-bearing plant yet it is mostly propagated vegetatively due to formation of sterile pollen grains thereby making pollination impossible. Cytogenetic study was carried out on collections of S. purpurea from the University of Lagos, Lagos, Nigeria. Chromosomal behaviour in the microsporocytes during meiosis was studied. Immature flower buds of S. purpurea were dissected in a Petri dish containing tap water. The microsporocytes were squashed using lactic acetic orcein stain. Most microsporocytes observed from slides contained 12 bivalents. However, a few contained 10 bivalents and one quadrivalent or 8 bivalents and 2 quadrivalents. This shows that 2n = 24 in the microsporocytes. Other irregularities observed included laggards, abnormal disjunction, chromosome bridges and chromosome fragments all at anaphase-1 and micronuclei at telophase-1. Occurrence of laggards, chromosome bridge formation and micronuclei were low ranging from 1 to 3 in the population of S. purpureastudied. The consequence of these irregular chromosomes is their loss and non-inclusion in the daughter nuclei at telophase-I. The loss of these segments would result in loss of genes on them resulting in the unviable microspores at the end of meiosis. These microspores are the pollen grains in which a large number of them have been found to be sterile.