Proteins, Sugars and Ion Leakage as a Selection Criterion for the Salt Tolerance of Three Sorghum Cultivars at Seedling Stage Grown Under NaCl and Nicotinamide

The interactive effects of salinity stress (0.90 MPa NaCl) and seeds presoaking in 100 ppm. nicotinamide (vitamin PP) in three sorghum cultivars (Dorado, Hagen Shandawil and Giza 113) were studied to examine their response to salinity stress and the possible role played by vitamin PP in regulating saltinduced changes in seedling growth, protein patterns and some relevant metabolic activities of these cultivars. According to the dry mass production and tissue water content, the cv. Dorado seemed to be more or less unaffected by salinity, whereas the cv. Giza 113, was severely reduced, the cv. Hagen Shandawil was almost intermediated. Consequently, carbohydrate and protein contents were increased in cv. Dorado and Hagen Shandawil, while the opposite occurred in cv. Giza 113. On the other hand, while proline content decreased in cv. Hagen Shandawil and Giza 113, it markedly increased in cv. Dorado as a result of salinity stress. Na / K ratio was higher in cv. Dorado than in cv. Giza 113. cv. Hagen Shandawil was intermediate. Treatment with vitamin PP was accompanied with higher values of saccharids and protein compared with the untreated seedlings, which partially alleviated the adverse effect of salinity on growth. This was linked with a marked variation in protein patterns among these cvs. Salinity stress led to the appearance of 67 and 26 kD (in cv. Dorado) and 45 kD (in cv. Hagen Shandawil). While in cv. Giza 113, no new band appeared. Seeds treated with vitamin PP lead to appearance of bands with 67 and 46 kD in cv. Dorado and 38, 26 and 18 kD in cv. Hagen Shandawil, while in cv. Giza 113, the 67 and 26 kD which had disappeared by salinity, they reappeared under the interactive effect of salinity and vitamin PP. This confirms the metabolic importance of the 67 and 26 kD proteins in salt tolerance.