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

Yamashita, K.; Kasai, M.; Yamamoto, Y.; Matsumoto, H.

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

1997

Yamashita, K. | Kasai, M. | Yamamoto, Y. | Matsumoto, H.

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.

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