Distribution of cations in leaves of salt‐tolerant and salt‐sensitive lines of sunflower under saline conditions

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Abstract
Two lines of sunflower (Helianthrus annuus L.), a salt‐tolerant Euroflor and a salt‐sensitive SMH‐24, were grown for three weeks in sand culture containing 0 or 150 mol/m3 NaCl in full strength Hoagland nutrient solution. Distribution of cations in the leaves of varying ages was determined. The older leaves of SMH‐24 contained more sodium (Na) in the laminae than the younger leaves at the salt treatment, whereas laminae of leaves of varying ages of Euroflor maintained Na concentration almost uniform. Distribution of potassium (K), calcium (Ca), and magnesium (Mg) in the laminae was strongly age‐dependent in both lines, i.e., the older leaves contained greater concentrations of these cations than did the younger leaves. The lines did not differ in concentrations of the three cations. The older leaves of SMH‐24 had significantly lower K/Na ratios than those of Euroflor, but the lines did not differ in lamina Ca/Na ratios. It is concluded that distribution of K, Ca, and Mg in the leaf laminae is age‐dependent. Salt‐tolerance in sunflower is related to exclusion of Na in the leaf laminae and to maintenance of almost uniform concentrations of this ion in leaves of all ages.