Variation of histological patterns in tobacco callus during successive subcultures

Abstract

Stem pith sections from haploid, diploid, and polyploid plants of Nicotiana tabacum L. cv. Wisconsin-38 were cultured in dark or light, in RM-64 medium with different auxin–cytokinin balances, and were subcultured four times. An analysis of the distribution of five histological types in the calluses was made. Growth, external morphology, and structural pattern were closely related to the conditions of culture. When cultured in medium with 2.0 mg/L indoleacetic acid plus 0.2 mg/L kinetin, in the dark, the primary calluses exhibited marked differences in growth, external morphology, and histological pattern depending on the original ploidy. These differences disappeared after several subcultures, all calluses becoming compact with similar internal structure.