Abstract:The relationship between glycine oxidation and nitrate reduction was studied using tobacco (Nicotiana tabacum L.) leaf disks and reconstituted system of isolated mitochondria and NR (Nitrate reductase). It was found that glycine, either vacuum-infiltrated in to leaf disks or added to the reconstituted system, could increase the rate of nitrate reduction. The stimulating effect of glycine on nitrate reduction was greatly influenced by preillumination treatment of tobacco leaves, and also by the activity of respiratory chain. The rate of glycinedependent O2 consumption by mitochondria was lowered when KNO3 and NR were added to the system. It was also found that the activity of glycine decarboxylase increased with increase in nitrate concentrations in the sandculture medium. It was concluded that oxidative decarboxylation of glycine in mitochondria of leaf cells of C3 plants could provide NADH for nitrate reduction in cytoplasm in the light, and nitrate reduction and glycine oxidation were influenced by each other.