The Release of Nitrite from Barley Roots in Response to Metabolic Inhibitors, Uncoupling Agents, and Anoxia

When excised sterile barley roots, from plants which had beengrown in the presence of nitrate, were placed under low oxygentensions, nitrite was released into the external solution. Themaximum leakage of nitrite occurred under completely anaerobicconditions. Nitrite was also released from barley roots underaerobic conditions when uncouplers of oxidative phosphorylation(DNP, CCCP¹, pentachlorophenol) or certain simple organic acidswere supplied. Inhibitors of the Krebs cycle, or of respiratoryelectron transport, were much less effective in causing theloss of nitrite, possibly because these compounds did not ingeneral inhibit root respiration severely. Nitrite release, in response to any of the above treatments,was accompanied by an accumulation of nitrite within the tissue.It was concluded that an increase in membrane permeability,and a decrease in ATP synthesis, were contributory causes ofthis phenomenon, although neither could explain the experimentalobservations completely. There was however no evidence thatthe pentose phosphate pathway, which is regarded as the sourceof reducing power for nitrite reduction, was inhibited underconditions which favoured nitrite release.