Potassium Affects Sodium Content in Tomato Plants Grown in Hydroponic Cultivation under Saline-sodic Stress

The tomato cultivars Edkawi and UC 82B ( Lycopersicon esculentum Mill.) were grown hydroponically in a solution [electrical conductivity (EC) 2.4 dS·m -1 ] containing 150 m m Na (EC 11.4 dS·m -1 ), 37 m m of K (EC 14.1 dS·m -1 ), or 75 m m of K (EC 19.7 dS·m -1 ). The leaf Na content of `Edkawi' and `UC 82B' reached values of 1717 and 2022 mmol·kg -1 dry weight at EC 19.7 dS·m -1 , respectively. The high levels of K in the hydroponic solution reduced the Na concentration in the roots, petioles, and stems, but not in the leaves. Potassium concentrations in the petioles of `Edkawi' and `UC 82 B' reached values of 2655 and 2966 mmol·kg -1 dry weight, respectively. At these elevated ECs, the Ca concentrations in the leaves of `Edkawi' and `UC 82B' were 30% and 40% lower than in the control, respectively. The elevated rates of K improved the fruit: flower ratio of `UC 82B', but the high salinity of the solution reduced yields significantly. Plant fresh weight and root dry weight of `UC 82B' were most affected by high EC levels. The elevated levels of K used in this study did not increase yield, but K ions can adjust to Na uptake.