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Environmental and Stress Physiology

Differential Inhibition by Ferulic Acid of Nitrate and Ammonium Uptake in Zea mays L. ¹

Department of Soil Science, North Carolina State University, Raleigh, North Carolina 27695-7619, Department of Botany, North Carolina State University, Raleigh, North Carolina 27695-7619

The influence of the allelopathic compound ferulic acid (FA) on nitrogen uptake from solutions containing both NO₃^– and NH₄⁺ was examined in 8-day-old nitrogen-depleted corn (Zea mays L.) seedlings. Concurrent effects on uptake of Cl^– and K⁺ also were assessed. The presence of 250 micromolar FA inhibited the initial (0-1 hours) rate of NO₃^– uptake and also prevented development of the NO₃^–-inducible accelerated rate. The pattern of recovery when FA was removed was interpreted as indicating a rapid relief of FA-restricted NO₃^– uptake activity, followed by a reinitiation of the induction of that activity. No inhibition of NO₃^– reduction was detected. Ammonium uptake was less sensitive than NO₃^– uptake to inhibition by FA. An inhibition of Cl^– uptake occurred as induction of the NO₃^– transport system developed in the absence of FA. Alterations of Cl^– uptake in the presence of FA were, therefore, a result of a beneficial effect, because NO₃^– uptake was restricted, and a direct inhibitory effect. The presence of FA increased the initial net K⁺ loss from the roots during exposure to the low K, ammonium nitrate uptake solution and delayed the recovery to positive net uptake, but it did not alter the general pattern of the response. The implications of the observations are discussed for growth of plants under natural conditions and cultural practices that foster periodic accumulation of allelopathic substances.