NITRATE REDUCTASE IN BARLEY ROOTS UNDER STERILE, LOW OXYGEN CONDITIONS

Levels of nitrate reductase activity (EC 1.9.6.1) as high as 11 .mu.mol NO2 produced/h fresh weight found in barley (Hordeum vulgare cv. ''Compana'') roots grown under low O2 conditions. Roots of plants given identical treatment under sterile conditions did not develop the high levels of nitrate reductase activity. The results suggest that the buildup of particulate, reduced viologen-utilizing nitrate reductase reported in barley roots may be caused by bacterial contamination. The nitrate reductase activity in roots grown under low O2 conditions was not specific for NADH like the assimilatory nitrate reductase (EC 1.6.6.1.) normally found in aerated plant roots.