Further Experiments on the Low Frequency Excess Noise of the Vacuolar Resting Potential of Chara braunii

The use of the low frequency (0.1–1.0 Hz) power spectraldensity function of the vacuolar resting potential is here appliedto the examination of a number of conditions which might beexpected to influence the active transport of ions. Once again,spectra of the form A/fµif are encountered. µifand p, the total power in the band, are significantly reducedby cyanide and by cyanide + salicylhydroxamic acid, but notby O₂ deprivation, µif and p are powerfully reduced byimidazole and reduced to a lesser extent by 1, 10-phenanthroleneand DCMU. The effects of darkness and deprivation of O₂ and/orCO₂ could not be told from the effects of darkness alone. Theresults of varying the external pH were not unambiguous butdo suggest that µif is maximal near pH 7.35 and that itfalls off for more acidic or more basic values. The implicationsof these spectra arc discussed.