DOES PATTERN OF ION ACCUMULATION VARY IN ALFALFA AT DIFFERENT GROWTH-STAGES

AZ-Germ Salt II, a salt tolerant line of alfalfa (Medicago sativa L.) at the germination stage, was compared with its parent line Mesa Sirsa in sand culture at the germination and seedling stages and in hydroponic culture at the adult stage under greenhouse conditions. The sodium chloride (NaCl) treatments used were 0 or 100 mol/m(3) in half strength Hoagland nutrient solution. AZ-Germ Salt II was superior to Mesa Sirsa in biomass production at all three stages. AZ-Germ Salt TI had significantly greater chloride (Cl) in the plumules and radicle than Mesa Sirsa at the germination stage. The two lines did not differ in shoot and root sodium (Na) and shoot Cl at the seedling stage. However, at the adult stage AZ-Germ Salt II accumulated significantly higher Na in the shoots and roots and Cl in the shoots compared with Mesa Sirsa. The two lines did not differ in tissue potassium/sodium (K/Na) ratios in all three experiments, although K concentrations were higher in the seedling shoots and roots, and in the plumules of AZ-Germ Salt II than Mesa Sirsa. The K versus Na selectivities were higher in the plumules and seedling shoots and roots of AZ-Germ Salt II compared with Mesa Sirsa, whereas at the adult stage the reverse was true. The lines also did not show any difference in tissue calcium (Ca) concentrations at any stage. It is concluded that salt tolerance in these two lines is not age-dependent. The pattern of ion accumulation varies with the change in growth stage. Generally there is a positive correlation between Na and Cl accumulation and growth in alfalfa.