Inorganic Nitrogen Metabolism in Barley Roots Under Poorly Aerated Conditions

Abstract

Nitrate reduction, nitrite reduction, and ammonium assimilation were measured over c. 24 h in excised sterile barley roots, in air or under low oxygen tensions. Partial anoxia had relatively little effect, but the pathway of nitrogen assimilation was severely inhibited during complete anoxia, when the uptake of nitrate ceased. Much of the nitrate which was present in the roots at the time of excision was apparently unavailable for assimilation. None of the reactions of the pathway served in place of oxygen as an electron acceptor under anaerobic conditions. The concentration of nitrate in the external solution during growth and during the experimental treatments had no direct effect on anaerobic ethanol formation, although an indirect effect was noted which was due to variations in the carbohydrate content of the tissue.