Abstract
Spinach leaf discs were floated on fluoride-containing solutions, and then extracted in the dark, or after 12–15 min illumination in saturating CO 2 . Fluoride led to a 4-5-fold increase of pyrophosphate, accumulation of hexose phosphates and UTP, depletion of UDP glucose, increased fructose 2,6-bisphosphate, and a selective restriction of photosynthetic sucrose synthesis. The effect of fluoride on the light-saturation curve and the induction kinetics of photosynthesis are consistent with the decreased rate of sucrose synthesis making a significant contribution to the inhibition of photosynthesis found in these conditions. The sensitivity of sucrose synthesis to fluoride was compared to the inhibition of glycolysis at the classic site at enolase, by measuring the change of the 3-phosphoglycerate-to-2-phosphoglycerate ratio. Similar concentrations of fluoride are needed for both effects. Fluoride also led to a selective net loss of the uridine nucleotides, but not of adenine nucleotides, and also decreased the activation of sucrose phosphate synthase. These results are discussed in terms of the significance of pyrophosphate for the control of cytosolic metabolism in higher plants.
Published Version
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