FLUORIDE METABOLISM IN ACACIA GEORGINAE GIDYEA.

1. The metabolism of fluoride in seedlings and small plants of Acacia georginae has been studied with the idea of finding the conditions under which the plant makes fluoroacetate in the laboratory. 2. Individual seedlings vary in the extent to which they take up fluoride and convert it into a form other than inorganic which is here called ;organic' fluoride, F(org.). The differences between the toxicity of A. georginae Gidyea trees may therefore be genetic in origin. 3. The uptake of fluoride from solutions 0.525-1.05mm (10-20p.p.m.) was not large. In 1-4 days it reached 8 p.p.m. in the aerial parts and 16 p.p.m. in the roots. Unlike the distribution of the halogen in grass, total fluoride was greater than inorganic fluoride. It was almost a rule that more ;organic' fluoride was present in the roots than in the aerial parts. 4. With higher concentrations of fluoride 10.5-15.75mm (200-300p.p.m.) much larger amounts of fluoride were taken up, especially by the roots, and much more apparent organic fluoride was formed. 5. pH had a large influence upon the intake, this being lowest at an initial pH8.4 and highest at pH4.0. The pH outside this range was not investigated. Some observations have been made with a view to clarifying the biochemical paths for the synthesis of the C-F bond. 6. There is no evidence that chloride is an intermediary in synthesis. 7. Succinate is not accumulated in fluoride-stressed plants, suggesting that succinate dehydrogenase is not inhibited. 8. Enolase does not appear to be inhibited in vivo.