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Metabolism and Enzymology

Control of PyrophosphateD-Fructose-6-Phosphate 1-Phosphotransferase Activity in the Cotyledons of Citrullus lanatus¹

Botany Department, University of the Orange Free State, Bloemfontein, South Africa

After initiation of radicle elongation, the pyrophosphate:D-fructose-6-phosphate 1-phosphotransferase (PFP) activity sharply increases in the cotyledons of Citrullus lanatus. Removal of the radicle early during incubation prevents the increase in PFP activity in the cotyledons evident in the control. Removal of the radicle at any stage after germination results in a decrease in PFP activity in the cotyledons. Application of kinetin (0.5 micromolar) or 2-chlorophosphonic acid (0.1 micromolar) to isolated cotyledons replaces the effect of the radicle. Gibberellic acid (0.09 micromolar GA₃) also partially mimics the presence of the radicle. Anaerobic conditions, as well as cycloheximide application (0.18 micromolar) to intact embryos or to kinetin and ethrel treated isolated cotyledons prevent the increase in PFP activity evident in the control.