Enhancement of nitrate efflux and the plasma membrane hydrogen ion‐transport activity of barley roots by nitrate treatment

Abstract

The effect of nitrate (NO₃) on the activities of hydrogen (H⁺)‐ATPase and H⁺‐transport in the plasma membrane vesicles isolated from barley (Hordeum vulgare L. cv. Kikaihadaka) roots was investigated. After treatment with 10 mM NO₃ for longer than 24 h, both activities of H⁺‐ATPase and H⁺‐transport assayed in the presence of chloride (Cl) were stimulated less than 20%. While H⁺‐transport activity was approximately two times higher in NO₃‐grown roots than in control roots when assayed in the presence of NO₃ instead of Cl. This result suggests that NO₃ is permeable in the plasma membrane vesicles isolated from NO₃‐grown roots rather than that of the control, and thereby stimulate H⁺‐transport activity through the collapse of positive potentials established by H⁺‐ATPase. Furthermore, NO₃ efflux from roots was markedly enhanced after 48 h of the exposure to NO₃. Taken together, NO₃ efflux may be mediated by the permeability to NO₃ which is induced by NO₃.

Notes

Corresponding author.