Effects of citrate on respiratory gas exchange and metabolism in carrot root tissues

This study was undertaken to determine the effects of citrate on respiratory gas exchanges and glycolytic metabolism in carrot root tissues (Daucus carota L.). Carrot root discs were incubated on media with citrate, and the resulting changes in the rates of CO2 production and O-2 consumption, and levels of glycolytic intermediates were monitored. Citrate inhibited the rates of CO2 production and O-2 consumption of carrot root tissues at concentrations higher than 1 mM. Fructose 6-phosphate accumulated and fructose 1,6-bisphosphate decreased in response to elevated concentration of citrate applied. These results suggest that citrate may inhibit the respiratory gas exchanges in carrot root tissues by inhibiting the phosphorylation of fructose 6-phosphate to fructose 1,6-bisphosphate. (C) 1997 Elsevier Science Ltd.