The Relationship Between Chromosome Volume and Dna Content in Unsquashed Metaphase Cells of Barley, Hordeum Vulgare Cv. Tuleen 346

Abstract

The present work used haploid and diploid cells of barley, Hordeum vulgare L. cv. Tuleen 346 (2n = 2x = 14), which has three reciprocal translocations. All seven chromosomes of the haploid set are distinguishable using morphological criteria in Feulgen-stained root-tip squashes seen in the light microscope, as are five of the bivalents at diakinesis. The relative DNA content per bivalent was estimated in pollen mother cells at diakinesis. The results showed that all seven chromosomes or bivalents of Tuleen 346 can be identified using relative DNA content as sole criterion. The absolute and relative volumes of the seven chromosomes were estimated from electron micrographs of serial sections of unsquashed root-tip cells of a haploid. The results show that, using relative chromosome volume as sole criterion, it is highly probable that all seven chromosomes in single unsquashed cells of Tuleen 346 can be correctly identified. Consequently, teats for various non-random spatial arrangements of chromosomes in unsquashed cells of Tuleen 346 using this character to identify the chromosomes should be feasible. There was a very highly significant positive relationship (r>0.99) between relative chromosome volume and mean relative DNA content per chromosome for each cell examined at metaphase of mitosis or meiosis. Thus, some mechanism ensures that the degree of condensation of all seven chromosomes within a cell is usually very similar in Tuleen 346, despite its grossly abnormal karyotype.