Salinity adversely affected the photosynthetic pigment biosynthesis and carbohydrate fractions in two broad bean lines, 67 and 13. The accumulation of proline and other amino acids was also altered. The interactive effects of salinity and exogenous treatments with vitamin pyridoxine (B6) on these parameters were also tested. These treatments included soaking the seeds or spraying the shoots with vitamin solution. The vitamin treatments generally counteracted the adverse effects of salinity. The importance of these treatments to the salinity tolerance of broad bean lines is discussed.
A gradual increase in NaCl concentration in the growth medium was used as a strategy to adapt sorghum plants (Sorghum bicolor L.) to relatively high concentrations of NaCl. over a period of 15 days, a low percentage (22.2%) of sorghum seeds germinated in 200 mM NaCl, but most of the seedlings obtained (85.8%) died. On the other hand, plants subjected to adaptation by a gradual increase in NaCl concentration in the growth medium became capable of growth in soil containing 300 mM NaCl. In general, salinization induced a highly significant decrease in fresh and dry masses, and in the pigment content of sorghum seedlings. The content of free amino acids and soluble carbohydrates increased with a rise in the salinization level, especially in the adapted sorghum plants. The adapted plants contained less Na+ but more K+ compared to the unadapted plants, especially when the plants were subjected to relatively high NaCl concentration. Plants adapted in soil showed a new peroxidase isoenzyme form (POX-4). The peroxidase band POX-1 was detected under salt stress in both adapted and unadapted plants. Under salt stress, indophenol oxidase and glutamate oxaloacetate transaminase expressed new isoenzyme forms, IPOX-3 and IPOX-5, and GOT-2 and GOT-3, respectively. The induction of salt tolerance by a gradual increase in NaCl concentration for three weeks was recommended to overcome the inhibition of seed germination in saline soil.
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