Variation for Salt Tolerance in Tobacco Cell Suspensions

Abstract

Cells of tobacco, Nicotiana tabacum cv. Wisconsin 38, have been obtained, which are capable of active growth in media with 10 or 25 g/1 NaCl (S-10 and S-25, respectively). The S-10 and S-25 cells, as well as a population of cells which had not been growing in salt (S-0), were evaluated for tolerance to salinity by examining their growth characteristics when inoculated into media with varying concentrations of NaCl. Tolerance of the cell populations to NaCl increased with the level of salt from which the cells were obtained. The enhanced tolerance of the S-10 cells was lost after one passage in the absence of salt, indicating that the tolerance of these cells was unstable. In contrast, the S-25 population retained a small but stable portion of its tolerance even after 40 recultures in the absence of salt. Analysis of the tolerance of individual clones isolated from the S-0 and S-10 populations indicated that substantial variation for salt tolerance exists within the cell populations, and that the S-10 population exhibited higher tolerances. The frequency distribution of tolerance for S-10 clones grown in the absence of salt was very similar to that of the S-0 clones. Increased tolerance of the S-10 cell population after exposure to salt appeared to be due to physiological adaptation since individual S-10 clones lost tolerance when grown in the absence of salt. The fact that the S-25 cells retained some degree of tolerance to salt suggests, that at high salt concentrations, it may be possible to identify both an unstable, adaptive component of tolerance, and a stable component which can withstand several recultures in the absence of salt.