The response of three wheat (
L.) cultivars Banysoif 1 (C1), Sakha 68 (C2) and Seds 1 (C3) to salinity stress (−1.11 MPa NaCl) at germination and early seedling growth was investigated. According to the germination, dry weight production and tissue water content, C1 seemed to be more or less unaffected by salinity, whereas C3 was severely reduced and C2 was almost intermediated. Consequently, carbohydrate, protein and free amino acids contents were increased in C1 and C2, while the opposite occurred in C3 (except soluble proteins and free amino acids). On the other hand, while proline content decreased in C2 and C3, it markedly increased in C1 as a result of salinity stress. Na
ratio was higher in C3 than in C1. C2 was intermediate. Significant increase in SOD activity was observed in seedlings of C1 and C2. On the other hand, SOD activity was markedly decreased in C3 cultivar. Seedling extracts exhibited three SOD activity bands (SOD1, SOD2 and SOD3) in C1 and C2. While in C3 seedling, only two SOD activity bands (SOD1 and SOD3) were identified, whereas the SOD2 isozyme was not expressed under control or NaCl conditions in this cultivar. Salinity stress significantly increased POD activity in C1 and C3, but it markedly decreased the activity of POD in C2. Two isozymes of POD (POD1 and POD2) were observed in all groups of C1. The intensity and density of POD1 and POD2 markedly increased under salinity stress versus control group. In C2, salinity stress resulted in disappearance of POD1 as compared with control group. In C3, salinity stress induced the appearance of POD1 which disappear under control group. CAT activity in C1 and C2 was markedly increased under NaCl salinity. On the other hand, CAT activity was markedly decreased in C3. NaCl salinity did not affect APX activity in three wheat cultivars. In addition, lipid peroxidation level of salt-sensitive C3 markedly increased, indicating more damage to membrane lipids due to −1.11 MPa NaCl. Lipid peroxidation did not change in the salt-tolerant C1 at the same concentration of NaCl. C2 was intermediate.These results suggest that at seedling stage, C1 is appeared to be more tolerant than C2 and C3 under salinity stress.
The salt tolerance of three sorghum (Sorghum bicolor L.) cultivars (Dorado, Hagen Shandawil and Giza 113) and their responses to shoot spraying with 25 ppm IAA were studied. Salinity stress induced substantial differences between the three sorghum cultivars in the leaf area, dry mass, relative water content and tolerance index of the leaves. Dorado and Hagen Shandawil tolerated salinity up to 88 and 44 mM NaCl, respectively, but above this level, and at all salinity levels in Giza 113, a significant reduction in these parameters was recorded. The rate of reduction was lower in Dorado than in Hagen Shandawil and Giza 113, allowing the sequence Dorado ? Hagen Shandawil ? Giza 113 to be established for the tolerance of these cultivars to salinity. The differences in the tolerance of the sorghum cultivars were associated with large differences in K+ rather than in Na+, which was found to be similar in the whole plant. The youngest leaf was able to maintain a higher K+ content than the oldest leaf. Consequently the K+/Na+ ratios were higher in the most salt-tolerant cultivar Dorado than in the other sorghum cultivars, and in the youngest than in the oldest leaf. In conformity with this mechanism, the stimulatory effect of the exogenous application of IAA was mostly associated with a higher K+/Na+ ratio. Shoot spraying with IAA partially alleviated the inhibitory effect of salinity on leaf growth and on the K+ and Ca2+ contents, especially at low and moderate levels of salinity, while it markedly retarded the accumulation of Na+ in the different organs of sorghum cultivars. Abbreviations: LA: Leaf area, DM: Dry mass, I Indole acetic acid, RWC: Relative water content,TI: Tolerance index