THE REGULATION OF EXPRESSION OF CELLULAR PHENOTYPES IN CULTURED TISSUE OF TOBACCO

Abstract

Persistent but reversible changes in the phenotype of a tobacco callus are reported in this paper. The callus (S401) was first isolated as a spontaneous variant which differed in pigmentation (dark grayed green) and friability (very friable and wettish) from its parent callus S4 (yellow and firm) during subculture on Murashige and Skoog medium with 2, 4-D. The callus consisted mainly of small embryonic cells and contained a high level of pectin, especially of water soluble forms, as compared with the S4 callus. Almost no lignified vascular elements were observed.
2, 4-D removal from the medium was accompanied by an increase in lignin and a decrease in pectin content. Peroxidase activity in the callus was low, but the level increased during subculture on the medium without 2, 4-D. Isozymes of peroxidase found in the callus after 2, 4-D removal were the same as those in the S4 callus. When the tissues of S401 grown on the 2, 4-D free medium were placed back on the medium with 2, 4-D, they recovered its original characters. The regenerated plant originated from the S401 callus produced only the S401 type callus.