Ion distribution in leaves of salt-tolerant and salt-sensitive lines of spring wheat under salt stress

Two lines of spring wheat, salt-tolerant S24 and salt-sensitive Potohar, were grown until the onset of ear formation in sand culture containing 0 or 125 mol m(-3) NaCl in full strength Hoagland's nutrient solution. Distributions of Na, K, Ca, Mg, and Cl in leaf laminae and leaf sheaths at varying ages were determined. Accumulation of Na and Cl in the laminae and sheaths of both lines increased significantly with age at 125 mol m(-3) NaCl. However, the older laminae and all sheaths of Potohar contained more Na and Cl than those of S24 at the NaCl treatment. There was no effect of age on the distribution of K in laminae and sheaths under NaCl stress. In the salt treatment, lamina K concentration did not differ significantly between lines, whereas sheath K was significantly greater in Potohar than S24. An age-dependent distribution of Ca was observed in laminae of both lines at NaCl treatment, i.e. the younger laminae had slightly lower concentration of Ca than the older leaves. S24 had significantly lower Ca in the sheaths of varying age compared with Potohar, but no such difference was observed in lamina Ca. S24 maintained relatively lower concentrations of K in the sheaths and culms at the NaCl treatment, most of this ion absorbed being transported to the laminae. S24 and Potohar did not differ in K/Na or Ca/Mg ratios in laminae and sheaths, and the pattern of these ratios was uniform in relation to age under salt stress. It is concluded that maintenance of low Na and Cl concentrations in laminae, sheaths of all ages and of culms is an important component of salt tolerance in spring wheat, and the distribution of Na, Cl, Ca, and Mg in the laminae and that of Na, Cl and Mg in the sheaths are age-dependent.