Oxygen consumption by purified plasmalemma vesicles from wheat roots

Plasmalemma vesicles from wheat (Triticum aestivum L.) roots consumed O2 and the addition of 1 mM NADH increased the rate ~ 3‐fold (to 15‐30 nmol O2·mg−1·min−1). The NADH‐dependent O2 uptake was abolished by catalase. In the presence of salicylhydroxamic acid (SHAM), an inhibitor of the alternative oxidase pathway in plant mitochondria, NADH‐dependent O2 consumption was stimulated 10–20‐fold (to 200–400 nmol·mg1̄·min−1). Catalase also abolished this stimulation, which was KCN‐sensitive but antimycin A‐insensitive, and the production of H2O2 during SHAM‐stimulated NADH‐dependent O2 uptake was demonstrated. Irrespective of the mechanism, SHAM‐stimulated respiration by root plasmalemma makes it difficult to interpret results on root respiration obtained using KCN and SHAM.