In vitro Cellular Salt Tolerance of Troyer citrange: Changes in Growth and Solutes Accumulation in Callus Tissue

Salt tolerant cell lines of Troyer citrange were obtained by exposing calli to increasing concentrations [0 - 8 g L-1] of NaCl. At 6 and 8 g L-1 NaCl, the morphology and growth of the tolerant calli were similar to the control maintained in salt-free medium, but in meanwhile the sensitive wild-type calli show salt injury symptoms resulting in tissue browning and drastically inhibited growth. The selected cell lines maintain their growth after transfer to salt-free medium and after retransfer to salt-containing medium, respectively indicating the independence and the stability of the salt tolerance. The implication of accumulation of both inorganic (Na+, K+) and organic (proline, soluble sugars) solutes were also evaluated. K+ content of the selected tolerant lines was close to that of the control and together were greater than that of the sensitive calli. But Na+ content in both tolerant and sensitive calli was relatively higher than in the control. Subsequently sodium has been accumulated in two cellular levels according to the calli types: vacuolar sequestration for the tolerant calli (halophytic behavior) and cytosol invasion for the sensitive calli. Increased vacuolar Na+ concentrations have been supported by increased accumulation in proline and soluble sugars, which are compatible solutes in the selected tolerant but not in the sensitive wild-type calli. © 2010 Friends Science Publishers