Studies in the Respiratory and Carbohydrate Metabolism of Plant Tissues1

Abstract

When specifically labelled glucose was fed to strawberry leaves, the C₆/C₁, quotient (rate of release of ¹⁴CO₂ from glucose-6-¹⁴C/rate of release of ¹⁴CO₂ from glucose-1¹⁴C ranged from 0.27 to 0.35 in leaves in water and from 0.46 to 0.96 in leaves fed with iodoacetate. These quotients indicate that both the glycolytic and the pentose phosphate pathways participate in the respiration of strawberry leaves, with a greater contribution from the former in the iodoacetate increased CO₂ output. Concurrently with the increase of CO² output in iodoacetate, the contents of glucose-6-phosphate (G6P), fructose-6 (F6P) and fructose-1,6-diphosphate (FDP) increased greatly; there was a smaller increase of phosphoenol-pyruvate (PEP). The increase in the CO₂ output in iodoacetate may be explained solely on the basis that the increases of G6P and FDP accelerate the rates respectively of the pentose phosphate pathway and of glycolysis and traffic into the tricarboxylic acid cycle. The increase in content of G6P and FDP is attributed to an increase in the accessibility of enzymes and substrates caused by iodoacetate. Alternatively the increased CO₂ output in iodoacetate may be partly due to uncoupling of oxidative phosphorylation.