Improvement of cellular salt tolerance of 'Troyer' citrange in vitro.

摘要

Selected cell lines of 'Troyer' citrange were developed by exposing calli to increasing concentrations of NaCl. At 8 g L-1 of NaCl the morphology and growth of the salt tolerant calli were similar to the control callus maintained in salt-free medium, whereas the sensitive wild-type calli expressed salt injury symptoms resulting in tissue browning and drastically inhibited growth. The selected cell lines maintained 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 accumulation of Na+, K+, Proline and soluble sugars solutes in the citrus cells were also quantified. K+ content of the selected tolerant cell lines was close to that of the control and higher than that of the sensitive calli. Na+ contents in both tolerant and sensitive calli were relatively higher than in the control. Subsequently, we concluded that sodium was accumulated in two distinct cellular compartments according to the callus types: in the vacuole for the tolerant calli (halophytic behavior) and in the cytosol for the sensitive calli. Increased vacuolar Na+ concentrations were supported through increased accumulation of Proline and soluble sugars which were compatible solutes in the selected tolerant but not in the sensitive calli.