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.
Potential objectives for gibberellic acid and paclobutrazol under salt stress in sweet sorghum (Sorghum bicolor [L.] Moench cv. Sofra)
