Heterochromatin at the Distal Ends of the Chromosomes in Triticum monococcum

Abstract

Kihara and Katayama¹ and Chizaki² studied meiosis in haploid Triticum monococcum (n = 7) and found that the chromosomes often become attached end-to-end, especially during diakinesis. It seemed very improbable that so many duplications or interchanges are responsible for this chromosome behaviour in the haploid T. monococcum. I suspected that this phenomenon is probably due to associations between heterochromatic regions of non-homologous chromosomes^3,4. In studying this problem, I fixed root tips of T. monococcum in one part 1 per cent platinum chloride with one part commercial formalin and stained the preparations with Newton's gentian violet. In the chromosome plates of the preparations, stained somewhat more deeply than usual, I found that small portions of the distal ends of almost all chromosomes remained dark, while all the other parts became lighter (being very deeply stained). In the accompanying illustration are shown several chromosomes drawn separately from one and the same metaphase plate. Only the lighter and the darker regions are indicated.