The effect of NaCl on proline accumulation in potato seedlings and calli

The effects of salt stress were Studied on the accumulation and metabolism of proline and its cot-relation with Na+ and K+ content in shoots and callus tissue of four potato cultivars, Viz., Agria, Kennebec (relatively salt tolerant), Diamant and Ajax (relatively salt sensitive). Na+ and proline contents increased in all cultivars under salt stress. However, K+ and protein contents decreased in response to NaCl treatments. The activities of enzymes involved in prolinc metabolism, Delta(1)-pyrroline-5-carboxylate synthetase (P5CS) and proline dehydrogenase (ProDH) increased and decreased, respectively, in response to elevated NaCl concentrations. The changes of P5CS and ProDH activities in more salt sensitive cultivars (Diamant, Ajax) were more than those in the tolerant ones. Then the stimulation of synthesis in combination with a partially increase of protein proteolysis, a decrease in proline utilization and inhibition of oxidation resulted in high proline contents in seedlings and calli Under salt stress. In callus tissue, reduced growth and cell size may be partially responsible for high proline accumulation in response to high NaCl levels. However, although the basic proline contents in the seedlings of more salt tolerant cultivars were higher than the sensitive ones, a clear relationship was not generally observed between accumulation of proline and salt tolerance in potato.