Interphase nuclear size variations in somatic and cultured tissues

--A. Kumar, H. Kumar and S. K. T. Nasar

Root explants from some selected inbred and hybrid genotypes, Tuxp124-1, Tuxp162-1, Tuxp46-6, Tuxp237-2, Tuxp104-2, MS1DR-120, PKMS1-49, Tuxp162-1xTuxp237-2, Tuxp162-1xTuxp124-1, Tuxp237-2xTuxp124-1, Tuxp104-2xTuxp46-6, MS1DR-120xPKMS1-49, of maize were exposed to callusing in Murashige and Skoog's basal medium supplemented with 2,4-dichlorophenoxyacetic acid (3.0mgL-1) and kinetin (2.0mgL-1).

The diameters of interphase nuclei, reflective of nuclear volumes, of root meristem cells, and the cells of calli developed from root explants were subjected to a comparative study. The frequency distribution of differently sized interphase nuclei among root meristems and calli of different genotypes was also compared.

Among the genotypes studied, the mean nuclear diameter ranged between 67.368� for genotype MS1DR-120 root tip cells and 8.522� for genotype Tuxp104-2xTuxp46-6 callus tissue cells. On the whole the callus nuclei were smaller in size compared to the root cell nuclei. For the root tip nuclei, the hybrids showed larger sizes than those of their parents.

The frequency distribution of variously sized interphase nuclei gave an insight into the distribution of G1, S and G2 nuclei in analogous populations. Root meristems showed normal to near normal distribution in comparison to highly skewed to bimodal distribution in analogous callus tissues.

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