Abstract
Seedling of Sorghum bicolor L. were grown hydroponically in growth units, filled with continuously aerated half strength of Hogland-nutrient solution. Different treatments were manipulated to determine the combined effect of three NaCl levels (30, 60 and 90 mM) with combined levels of Ca2+ : K+ : Mg2+ (10: 12: 3 mM) on seedling growth. Seedling length, leaf sap osmolality, total chlorophyll, soluble protein, proline, phosphpenolpyruvate carboxylase (PEPC) andsucrose phosphate synthase (SPS) were used as reaction criteria. Several ions (Na+, K+, Ca2+ and Mg (2+)) were analysed in seedling material. Saline treatments decreased the growth, which was partly restored with the cation ratio treatment. A significant relation was observed between the electric conductivity of the nutrient solution and the osmolality of leaves using independent treatment (salinity or cation ratio). Salinity at all concentrations used in this work were reduced the total chlorophyll and soluble protein yield compared with that obtained at 0 mMNaCl. However, there was an increase, of previous criteria, as a consequence of the application of cation ratio treatments in each saline concentration. Higher concentrations of proline in shoot were obtained with increasing salinity concentrations. PEPC enzyme activity in roots was considerably higher than shoot under salt medium as well as with cation treatments. Both shoot and root SPS activities were slightly higher in root than in shoot subjected to salt and cation treatments. At high NaCl concentration, the ratio Na/Ca and Na/Mg decreased as a consequence of cation treatments. Therefore, the cation combination treatments were applied in the nutrient solution could be important factors in the hydroponic culture of sorghum grown under saline conditions.