Explants are generally taken from any tissue, namely leaves, internodes, ovaries, roots; and inflorescences. The source of the explant has been considered a critical variable for somaclonal variation. It is likely that different selective pressures would be exerted against different explant resources in culture, resulting in the spectrum of soma clonal variation among regenerated plants.

Many established cell cultures show chromosomal mosaicism. Several factors contribute to variation in the chromosome number such as

1) preexisting chromosome mosaicism (polysomaty the phenomenon of polyploidization of body cells) in explants used for culture initiation,

2) nuclear fragmentation associated with first cell division of callus initiation,

High proportions of growth regulators effect karyotypic alterations in cultured cells. 2, 4-0, BAP, and others have been shown to induce chromosomal variability in cultured cells, leading to the formation of somaclones.

Growth hormones are essential for induction of organogenesis and shoot differentiation; however, high concentrations of these substances may not permit recovery of whole plants in tissue cultures and the proportion of hormones in the medium needs to be carefully monitored in establishing culture systems for in vitro propagation of somaclonal variants.