Chromosome banding and heterochromatin in Vicia faba.

The distribution of bands in Vicia faba (broad bean) root-tip chromosomes as shown by acid treatment, quinacrine mustard fluorescence, SSC-Giemsa banding and orcein banding is documented. These bands coincide with the position of heterochromatin revealed by cold treatment. Heterochromatin in the large M chromosome is located in two areas: (a) around the centromere and (b) adjacent to the secondary constriction. Heterochromatin in the smaller, sub-telocentric S chromosomes is located in the intercalary and proximal areas of their long arms and in the short arm of two chromosomes. Most of the observed bands were not exclusive to one treatment but could be recognized in chromosomes prepared by several methods. The variable expression of particular chromosome segments with different banding techniques testifies to the existence of several classes of heterochromatin.