Meiotic behaviour of chromosomes and the nature of ploidy in four species of Commelina (Commelinaceae) from Bangladesh.

Abstract

Study of meiosis in the pollen mother cells showed n=30 in Commelina paludosa, n=30 and 60 in C. erecta, n=15 in both C. hasskarlii and C. diffusa. The presence of n=15 or its multiple in these species suggests that they have a basic chromosome number of x=15. Nearly regular formation of bivalents even in C. paludosa and C. erecta, suggests that they are either old established autopolyploid or allopolyploid. Majority of the bivalents in all these species were ring-shaped with mostly terminal chiasmata. The mean chiasma frequency per bivalent and mean chromatin surface area per bivalent respectively were 1.71±0.04 and 9.34±0.38 in C. paludosa, 1.76±0.03 and 8.85±0.46 in C. erecta, 1.79±0.04 and 9.73±0.44 in C. hasskarlii and 1.83±0.05 and 6.89±0.39 in C. diffusa. The absence of any correlation between the mean chiasma frequency per bivalent and the mean chromatin surface area per bivalent supports genetic control of chiasma formation.