Effect of Fluoride on Glucose Catabolism in Plant Leaves.

Various workers have studied the effect of fluoride on respiration rates of plant tissues (1, 7, 8, 9, 14, 18, 19, 22, 23). In some cases fluoride has been found to stimulate respiration and in others to inhibit it. Ordin and Jacobson (23) found a marked inhibition in oxygen uptake when barley roots were treated with fluoride concentrations of 0.002 M. Bonner and Wildman (7) observed similar results with spinach leaf discs. Applegate et al. (1) found that high fluoride concentrations inhibited respiration of bush bean seedlings but that seedlings infiltrated with lower concentrations (0.001-0.0001 M NaF) often respired faster than those infiltrated with water. The influence of fluoride was modified by light, COO, and the presence of chlorophyll. MIcNulty and Lords (19), working with Chlorella pyrenoidosa, also reported that while high concentrations of fluoride were inhibitory, lower levels stimulated oxygen uptake. The stimulation appeared to be related to the undissociated HF concentration in the suspending media. All concentrations of the NaF added caused increases in total nucleotide phosphate and it was suggested that increased respiration may have resulted from increases in phosphate donor or acceptor. Other workers have reported cases where fluoride did not decrease the respiration of various plant tissues. Christiansen and Thimann (9) reported increased rates in pea stem sections treated with a fluoride concentration which decreased growth of the sections nearly 50 %. Bonner and Thimann (8) found that amounts of fluoride sufficient to decrease growth of oat coleoptiles 50 % did not inhibit respiration rates. Nickerson and Chung (22) obtained similar results with yeast cells. McNulty and Newman (18) and Wiebe (unpublished results), working with leaves of plants previously injured by atmospheric fluoride, obtained respiration rates greater than in untreated leaves. Hill et al. (14) have made extensive studies on the effect of atmospheric fluorides on the respiration of several plant leaves. They found that some species could accumulate large amounts of fluoride with no effect on oxygen absorption. In their experiments the only