The influence of genomes on autonomous growth of pith cultures of Nicotiana glauca-Langsdorffii hybrids.

A differential influence of the two parental genomes on cell proliferation and morphogenesis in pith tissue explants can be observed among the various tumorous hybrid combinations between Nicotiana glauca Grah. and N. langsdorffii Weinm.: the F1 hybrid (GL), its amphiploid (GGLL), and two different triploids (GGL and GLL). This influence was evident when the explants were cultured in the presence of exogenous auxin (indole-3-acetic acid, 2.5 μM), supplied either continuously or for a brief period of time. Compared with the F1 and the amphiploid, the higher proportion of N. glauca genomes in GGL cells resulted in greater growth, the higher proportion of N. langsdorffii genomes in GLL cells in lesser growth. In addition, shoots are produced on the GGL callus, while only roots are formed on calli of the other types in the same medium. When, in addition to auxin, a cytokinin [6-(3-methyl-2-butenyl-amino)purine] was added to the culture medium, the differential growth of the different tissue types was less pronounced; at 1.0 μM of the cytokinin, all tissues grew at about the same rate and remained undifferentiated, regardless of their genomic composition.