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The Influence of Nitrate and Chloride Uptake on Expressed Sap pH, Organic Acid Synthesis, and Potassium Accumulation in Higher Plants ¹

^a Department of Agronomy, University of Kentucky, Lexington, Kentucky 40506

The influence of NO₃^– uptake and reduction on ionic balance in barley seedlings (Hordeum vulgare, cv. Compana) was studied. KNO₃ and KCl treatment solutions were used for comparison of cation and anion uptake. The rate of Cl^– uptake was more rapid than the rate of NO₃^– uptake during the first 2 to 4 hours of treatment. There was an acceleration in rate of NO₃^– uptake after 4 hours resulting in a sustained rate of NO₃^– uptake which exceeded the rate of Cl^– uptake. The initial (2 to 4 hours) rate of K⁺ uptake appeared to be independent of the rate of anion uptake. After 4 hours the rate of K⁺ uptake was greater with the KNO₃ treatment than with the KCl treatment, and the solution pH, cell sap pH, and organic acid levels with KNO₃ increased, relative to those with the KCl treatment. When absorption experiments were conducted in darkness, K⁺ uptake from KNO₃ did not exceed K⁺ uptake from KCl. We suggest that the greater uptake and accumulation of K⁺ in NO₃^–-treated plants resulted from (a) a more rapid, sustained uptake and transport of NO₃^– providing a mobile counteranion for K⁺ transport, and (b) the synthesis of organic acids in response to NO₃^– reduction increasing the capacity for K⁺ accumulation by providing a source of nondiffusible organic anions.

¹ This work represents a portion of a dissertation submitted to the Graduate School at the University of Kentucky in 1972, in partial fulfillment of the requirements for a Ph.D. degree. This paper (No. 73-3-116) is part of a project of the Kentucky Agricultural Experiment Station and is published with approval of the Director.