B Chromosomes in Spontaneous and Induced Intercellular Chromosome Migration of Papaver Somniferum L

Cytomictic subpopulations raised from mutagen-treated and untreated populations of Papaver somniferum (2n=22) show intraindividual variability for a chromosome numbers at both somatic and meiotic levels. Three B chromosomes, of whichh the first two are submetacentric (B₁ and B₂) and the third one telocentric (B₃, have been identified in these subpopulations. The B chromosoines, besides indicating their inhibitory effects on a chromosome size, appeared to be involved with their pioneering functions in intercellular chromosome migration. The heterochromatic elements identified in B chromosomes may be responsible for their kinetic activity and sticky associations with other chromosomes. Specific breakage at the proximity of the heterochromatic block of B₁ was considered to be doe to intracellular mobile function of the heterochromatic block. B chromocome-pioueered cytomixis is the possible underlying cause of derangements in chromosome number (4–39 in meiocytes, binucleate PMC, and large variations In pollen size in cytomictic subpopulations. The data on numerical variations in chromosomes coupled with low gametic sterility (12.63–38.45%) of cytomictic plants point to the fact that B-pioneered cytomixis may be playing an important role in the evolution of P. somniferum.