The regulation of pathways of glucose catabolism in maize roots

Abstract

The effects of artificial electron acceptors on the respiration of maize root-tips and on their release of 14CO2 from specifically labelled glucose in air and under N have been investigated. Meth-ylene blue, phenazine methosulphate and triphenyltetrazolium chloride each stimulated the production of CO2, with preferential release of 14CO2from [1-14C]glucose. In air, 14CO2 release from [2-14C] glucose was also stimulated. By comparison, 2:4-dinitrophenol increased the release of 14CO2 from [3:4-14C]- and, rather less, from [2-14c]-glucose, but decreased that from [1-14C] glucose. Treatment with nitrite gave effects similar to those with the artificial electron acceptors. It is suggested that the activity of the pentose phosphate pathway in this tissue is limited by the supply of oxidized triphosphopyridine nucleotide, and that nitrite reduction is coupled with its operation.