Karyotype and the Control of Interchromosome Distribution of Chiasmata

Observations on chiasma distribution in structurally homozygous and heterozygous plants of Chrysanthemum carinatum indicate that the different chromosome pairs form chiasmata in a positively correlated or non-correlated manner. In this respect, the present species is marked by a behaviour in complete contrast to that of Delphinium ajacis, whose chromosomes were earlier found to show negatively correlated chiasma formation. A comparison of the karyotype of the two species and other findings suggest that chromosome length and form are important factors in determining the nature of chiasma distribution among the different chromosome pairs.