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 mM Na (EC 11.4 dS.m(-1)), 37 mM of K (EC 14.1 dS.m(-1)), or 75 mM 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.