The effect of fluoride on the respiration of leaves fromChenopodium muraleand soybean Glycine max, Merr., Hawkeye variety) was studied. Fluoride treatment included both excised leaves cultured in nutrient solutions and leaves from plants fumigated with HP atmosphere. Tissues treated with low fluoride concentrations which initially showed increased oxygen uptake eventually showed decreased oxygen consumption. Tissues treated with a high concentration of fluoride showed an increased oxygen uptake if analyzed soon after treatment initiation. Increase in respiration generally took place before visible damage was manifested. Decrease in respiration was correlated with pronounced injury of tissues. Besides concentration of fluoride and the time lapse of treatment, the pH of the culture solution in which fluoride was supplemented, tissue age, and plant species, were important factors affecting respiration. The effect of 2, 4-dinitrophenol (DNP) on respiration was very similar to that of fluoride in that the effect differed with pH, concentrations, time of treatment, leaf age, and plant species. The respiration of fluoride treated leaves was stimulated less by DNP than that of control leaves.
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