EFFECTS OF NITRITE AND SULFATE ON K+ UPTAKE AND GROWTH OF WHEAT AND CUCUMBER SEEDLINGS

The uptake of K+ ion was studied in the roots of wheat (Triticum aesti vum L. cv. GK Szeged) and cucumber (Cucumis sativus L. cv. Budai oseme ge) seedlings grown in nutrient solution under nitrite and sulfate str ess conditions. Seedlings pretreated with 1 or 10 mM NaNO2 absorbed mo re K+(Rb-86) than those treated with 0.1 mM NaNO2. However, the postef fect was influenced considerably by Na2SO4 treatment. The results sugg est that at least a partial feed-back regulation of K+ uptake may occu r. However, due to the high Na+ content of the roots and the possible toxicity of NO2-, effects of Na+ and NO2- in this process cannot be ex cluded. The dry matter yields of the roots and shoots were strongly in fluenced by the NO2- supply of the plants. However, appreciable differ ences were observed between wheat and cucumber seedlings. The optimal SO42- and NO2- concentrations of the growth solution for maximal growt h differed considerably for the two species, and also for the roots an d shoots in a given species. The root growth was strongly inhibited by increasing NO2- concentrations, but the shoot development was favoura bly affected, indicating that plants can assimilate NO2- taken up by t he roots.