Cell lines of soybean were obtained from the plant stem callus culture adapted to 85 mM (5 gL-1 NaCl) before they were transferred to GB5 basal medium with different concentrations of NaCl (0.0, 171, 342, 513 and 684 mM). Cells were harvested for analysis each two weeks from the first day after inoculation in the desired concentration of NaCl. Cells could adapt to grow in media with concentrations of NaCl up to 40 g L-1 (684 mM). Salt-adapted cells exhibited an enhanced ability to gain both fresh and dry weight in the presence of NaCl. Not-adapted and adapted cells were influenced by the stage of growth, with highest degree of tolerance exhibited by cells in the exponential stages. Osmotic and water potentials of the cells increased during the growth cycle of the cells and with salinity. Adaptation of soybean cell suspension cultures to NaCl led to reduced fresh weight gain while dry weight gain remained unaffected. The reduction in cell's fresh weight was not due to failure to the cells to maintain turgor since cells adapted to NaCl underwent osmotic adjustment in excess of change in water potential. Tolerance of soybean cells appears to involve soluble sugars and total free amino acids and proline. Ions of Na+ and Cl- are principal components of cells osmotic adjustment.
Key words: Soybean (Glycine max), cell suspensions, NaCl salinity, osmotic and water potentials, growth parameters, organic and inorganic solutes, salt tolerance
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