Respiratory Characteristics of Isolated Barley Mitochondria and Intact Barley Roots

Purified mitochondria were prepared from roots of 7- and 14-d-oldbarley plants and their respiratory activities were determined.The following observations were made. (1) With age, total oxygenuptake declined in the intact root and in isolated root mitochondria.(2) The alternative pathway was present and engaged to 60% ofits capacity in the intact roots of both 7- and 14- d-old plants.In the isolated mitochondria its activity depended on the substrateused. (3) State 4 respiration rates were high in the isolatedmitochondria, but there was little contribution by the alternativeoxidase. The implications of these findings are discussed. Itis proposed that mitochondrial respiratory capacity plays animportant role in determining the respiration rate of the intactbarley root. Key words: Mitochondria, cytochrome path, alternative path, roots, barley