Mechanisms of salt tolerance in a cell line of Pisum sativum: Biochemical and physiological aspects

The mechanisms of adaptation to salt tolerance were studied by selecting cell cultures of two lines of Pisum sativum L. cv Challis, one salt sensitive and the other adapted to 85.5 mM NaCl. Calli adapted to NaCl (85.5 mM) differed from unadapted ones in their accumulation of organic solutes such as proteins, sugars, amino acids, organic acids and ascorbic acid. In response to NaCl, the intracellular levels of Na+ and Cl- increased in adapted calli and also the average concentrations of reducing sugars increased (the principal solutes for osmotic adjustment), as did total free amino acids and ascorbic acid. The enzyme activities related to sugar metabolism (glucose-6-phosphate dehydrogenase (EC 1.11.1.49), glucokinase (EC 2.7.1.2), fructokinase (EC 2.7.1.4) and acid invertase (EC 3.2.1.25) were determined in both cell lines as were enzyme activities of the proline metabolic pathway. The results suggest that calli adaptation to NaCl might depend on modification of the osmotic adjustment through reducing sugars, together with modification of physiological and biochemical parameters.