GROWTH, ION CONTENT AND PROLINE ACCUMULATION IN NACL-SELECTED AND NONSELECTED CELL-LINES OF LUCERNE CULTURED ON SODIUM AND POTASSIUM-SALTS

Batch suspension cultures of Lucerne (Medicago media cv Rambler), esta blished directly from surface-sterilized leaflet explants, were subcul tured into media of progressively higher salinity to produce a cell li ne tolerant to 400 mol/m(3) NaCl. After these cells were grown for eig ht passages (28 days each) on NaCl-free medium, the cells were still m ore salt-tolerant than non-selected cells when recultured to salt supp lemented media. The exposure of the NaCl-tolerant cell line to equimol ar concentrations of salts other than NaCl resulted in enhanced tolera nce to Na2SO4 or K2SO4 but limited tolerance to KCl. The salt-tolerant cell line showed enhanced Na+ exclusion and was able to maintain high er K+ and much lower Na+/K+ ratios than the non-selected cell line in response to NaCl or Na2SO4 stress. The proline concentration was much higher in the salt-selected compared with the non-selected cell line u nder NaCl or Na2SO4 stress. Proline accumulation did not result from K 2SO4 or KCl stress in either selected or non-selected cell lines, sugg esting this is a response to Na+ rather than Cl- or K+. The results su ggest that growth inhibition in selected and non-selected cells under KCl stress could result from the toxic effects of Cl-. (C) 1997 Elsevi er Science Ireland ltd.