CYTOLOGICAL CHANGES LEADING TO LOSS OF DIFFERENTIATION IN NIGELLA-SATIVA (RANUNCULACEAE)

A detailed study of the callus tissue of Nigella sativa at different a ges was carried out-to determine the cytological factors leading to th e loss of differentiation. The study revealed that abnormalities of ch romosome number (like tetraploidy, aneuploidy and very high degree of polyploidy) as well as structure (like binucleate cells, micronuclei, diplochromosome, multipolarity, sticky bridge and ring chromosome form ation) were directly proportional to age of the callus-tissues. The ab normalities might be due to endoreduplication and various disturbances during mitosis.