Division of Botany, Indian Agricultural Research Institute, New Delhi-12
Karyomorphology of S. ankolib var. annalib red was studied both at somatic metaphase in root tip cells and at pachytene in pollen mother cells. Idiograms of the somatic chromosomes are presented on the basis of relative length and centromere position. Pachytene chromosomes are depicted on the basis of relative lengths, centromere position, arm-ratio and number of chromomeres which are nearer to the darkly staining region. A close agreement between the two idiograms was noticed with regard to major factors like relative length, arm-ratio and position of the centromere. Both pachytene chromosomes and somatic chromosomes exhibit differential staining regions which persist till late diakinesis.
Studies on the pairing properties of the differentially stained regions show proximally that synapsis starts while separation of the split chromosomes starts from distal end. The distribution of chiasmata at different stages and the terminalization co-efficient was studied. A critical analysis of the bivalents at diakinesis revealed that chiasmata are absent or rarely present in the deeply staining region. If there is such a localization, it would mean recombination of the genes located in the heavily stained region would be highly restricted.
