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Changes in germination and early seedling growth of sorghum ( Sorghum bicolor (L.) cv. JS-263) were studied following incubation of caryopses for 24 h in various levels of NaCl. A decrease in the imbibition of water indicated osmotic effects and an increase in dry weight, soluble sugars, total proteins and free proline showed ionic toxicity. Germination of NaCl-incubated caryopses in water showed a decline over time in the level of free proline and was related to the dilution of ions, suggesting this accumulation was due to ionic toxicity. Soluble sugars and total proteins followed the same pattern, although they were not related to the dilution of ions and a major portion appeared to be partitioned to the production of plumule and radicle. Embryonic tissues partitioned a large portion of ions (Na + and Cl − ) to the mesocotyl, while other nutrients (K + , Ca, N and P) were partitioned to the plumule and radicle. Correlations of ionic and nutrient content of embryonic tissues with their elongation and dry weight revealed that K + , Ca, and P are the main determinants of growth. NaCl had no effect on the anatomy of the stelar region of embryonic tissues. Cortical cells of the mesocotyl were reduced in size and their walls were substantially thickened. It appeared that ionic toxicity had a greater effect, than osmotic on the growth of the embryo, as is evident during and after germination in water. Sorghum managed to escape the adverse effect of NaCl by partitioning higher levels of organic metabolites and beneficial nutrients to the plumule and radicle, and toxic ions presumably to the cortical region of mesocotyl. |
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