Photoinduced Changes in Electrical Potentials and H+ Activities of the Chloroplast, Cytoplasm, and Vacuole of Phaeoceros laevis

Davis, R. F.

doi:10.1007/978-3-642-65986-7_27

Cited by 36 publications

(14 citation statements)

References 11 publications

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“…Evidence for this possibility is the observed significant drop in internal pH that occurred in the dark. This effect has been noted by other researchers as well (7,22).…”

Section: Methodssupporting

confidence: 83%

Effects of Environmental pH on the Internal pH of Chlorella pyrenoidosa, Scenedesmus quadricauda, and Euglena mutabilis

Lane¹,

Burris²

1981

Plant Physiol.

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The effect of external pH on two laboratory-cultured acid-intolerant species (Chlorella pyrenoidosa Chick and Scenedesmus qudaa Turp.Breb.) and one acid-tolerant species from a natural population (Euglena mutabilis Schmitz) was examined by measuring internal pH. These measurements were made with the weak acid 'C-dimethyloxazolidine-2,4-dione after cels had been incubated for 2 and 6 hours at external pH levels from 3.0 to 8.0. Photosynthetic and respiration rates of the three species were also measured over the range of external pH levels.AU three species regulated their internal pH levels over the 6-hour incubation time. C. pyrenoidosa and S. qa had internal pH levels around 7.0, regardless of external pH. E. mutabilis had a wider internal pH range, from 5.0 at low external pH to 8.0 at high external pH. External pH had no effect on either photosynthetic or respiration rates. Statistical comparisons showed that there was a significant difference between the acid-intolerant and acid-tolerant species with regard to the level of internal pH maintained and the response of internal pH to external pH.Many streams in Pennsylvania and other parts of Appalachia have become polluted with H2SO4 from coal mines in the region. As a consequence, the pH levels in these streams are very low, in the range of 1.4 to 4.5 (6). The low environmental pH, along with other factors such as high acidity and high iron concentrations, strongly affects the biota of these streams (3). Algal species diversity is quite low (3, 24) and decreases as the pH level decreases. Nevertheless, certain species of algae flourish in these streams (3,10,24).Studies, such as those cited, have characterized a number of aspects ofnatural populations of these algae. However, little about the physiology at low external pH of acid-tolerant species is known.The measurement of internal (cytoplasmic) pH with ['4CJDMO2 provides one method by which the effect of external pH on a cell can be investigated (see Ref. 15 for a review of internal pH and methods of its measurement). None of the algae that have been studied with this method have been acid-tolerant species. Furthermore, internal pH levels have not been measured when external pH levels are as low as those encountered by acid-tolerant species.In this study, [(4CIDMO was 3.0 to 8.0. For comparative purposes, the internal pH levels of two laboratory-cultured acid-intolerant species were also measured over the same external pH range. The objective of the study was to determine whether or not the three species maintained constant internal pH levels regardless of external pH and whether there were differences between the internal pH levels ofthe acid-tolerant species and the acid-intolerant species.Results of the internal pH measurements indicate that differences do exist in both the actual values of internal pH that the acid-tolerant and acid-intolerant species have and in the way in which the internal pH of each species responds as external pH changes. MATERIALS AND METHODSOrganisms. The two acid-in...

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“…Evidence for this possibility is the observed significant drop in internal pH that occurred in the dark. This effect has been noted by other researchers as well (7,22).…”

Section: Methodssupporting

confidence: 83%

Effects of Environmental pH on the Internal pH of Chlorella pyrenoidosa, Scenedesmus quadricauda, and Euglena mutabilis

Lane¹,

Burris²

1981

Plant Physiol.

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“…In Riccia, the steady-state level of ATP in the light and dark, respectively, is not significantly different from a mean value of (300 +9)ng AYP/mg dry weight. From the cytoplasmic pH of another archegoniate cell, Phaeoceros laevis (Davis, 1974), EH(L ) and EH(D ) of the Riccia plasmalemma of + 59 and +65 mV, respectively, can be estimated. Then Eq.…”

Section: Discussionmentioning

confidence: 99%

Effect of light upon membrane potential, conductance, and ion fluxes inRiccia fluitans

Felle

Bentrup

1976

J. Membrain Biol.

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Summary. The membrane potential Era, slope conductance g,,, and fluxes of S6Rb+/K+ and 36C1-have been measured on cells of the aquatic liverwort Riccia fluitans in artificial pond water of pH 4 to 8 and 0.1 to 10 mM K +, in the dark and 1 mW/cm 2 of white light. In the dark, E m reflects a passive diffusion potential according to the Goldman equation with relative ionic permeabilities, Pn/PK/PNa = 10:1:0.02. In the light, E m of -200 to -240 mV exceeds the most negative ion diffusion potential, i.e. E~, by more than 100 mV, is more sensitive to H + than K +, and is reduced to the dark level by uncouplers of phosphorylation. At 1 mM K +, gm is 33 and 50 gS/cm 2 in the light and dark, respectively, gm is sensitive to Ho + only in the light, and more sensitive to K + in the dark. Current-voltage relationships are given. Light increases the influx at the plasmalemma of S6Rb+/K+ and 36C1 less than would be expected from the increase of E~. It is concluded that the electrogenic pump operates in the dark as a constant current source which is shunted by the diffusive channels, whereas in the light E m approaches the H +-dependent electromotive force of the electrogenic pump.The origin of the common notion that electrogenesis at the cell membrane of green plants utilizes photosynthetic energy may be dated back to the days of the founder of membrane biology, W. Pfeffer, whose coworker Haacke (1892) recorded light-induced voltages from green tissues of higher plants. In current hypotheses the plant cell membrane is represented by an electrical equivalent circuit which contains ion-specific passiv e diffusive elements in parallel with an ATP-powered electrogenic proton pump (see Slayman, 1974;Bentrup, 1975). However, the complex influence of light upon ion transport (see MacRobbie, 1971;Higinbotham, 1973), and furthermore, the intimate linkage of energy metabolism of the chloroplasts to that of the other cellular compartments (see Heber, 1974), renders unlikely that light acts only via ATP-consuming pumps, the passive elements being coupled only electrically to them. The regulation of cytoplasmic pH as outlined by Raven and Smith (1973), requires a more refined mode of control. In fact, Spanswick (1972), and Vredenberg and

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“…This possibility is, in fact, supported by the finding that the vacuole of Valonia is more acid in the light (pH 5.8) than in the dark (pH 6.5) (R. F. Davis, unpublished data). The pH gradient is probably in the wrong direction for the manifestation of Evc as an H+ diffusion potential if, as has been found in several plants, the cytoplasmic pH is close to 7 (7,29).…”

Section: Effects Of Concentration Changes Of Other Ions In Aswmentioning

confidence: 92%

“…would be -46 mv if the cytoplasmic pH is 7 (pH of ASW is 7.8). This conclusion is based on the observation that Euo becomes more negative as the external pH is decreased below 7, whereas it should change in a positive direction if the observed effect on Euo is the result of a change in a diffusion potential for Ee..…”

Section: Effects Of Concentration Changes Of Other Ions In Aswmentioning

confidence: 99%

Electrical Properties of the Plasmalemma and Tonoplast in Valonia ventricosa

Davis¹

1981

Plant Physiol.

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Studies were made on the electric potentials of the plasmalemma (Em.) and tonoplast (E,) in small cells (1-3 mm diameter) of Valonia ventricosa.To measure E,,,, microelectrodes with long tapers were inserted into the vacuole with the path of electrode entry off-center. The microelectrode then was pushed across the vacuole and into the cytoplasm on the opposite side of the cell. A reference electrode was placed in the artificial seawater bathing the cell. A similar method was used to measure E, except that the reference electrode was placed in the vacuole.Both E,, and E,,, were influenced by light. In the light, E¢o was -70 millivolts and it changed to -60 millivolts in the dark (cytoplasm-negative to outside). For E,,,, the potentials were +86 millivolts in the light and +69 millivolts in the dark (vacuole-positive to cytoplasm). The vacuole potential (E,.) was demonstrated to be the algebraic sum of E". and E,,,> For example, in the light, the sum of the means (±SE) for E>o (= -70 ± 1) and E,,, (= +86± ) is +16 millivolts, which is comparable to the measured E>o of +17 ± 2 millivolts. In the dark, the sum of E,. (= -60 ± 3) and E, (+69 ± 6) is +9 millivolts and the measured value of E"o is +9 ± 4 millivolts.The external K+ concentration had a controlling effect on both E". and the direct current resistance of the plasmalemma, which suggests that E,.. is largely a K+ diffusion potential. The tonoplast electrical properties were affected only slightly by external K+.The data presented are indicative of a K+ electrogenic influx pump in the tonoplast. It is also considered possible that H+ might be electrogenically pumped from the cytoplasm both into the vacuole and to the cell exterior.In 1924, Osterhout (25)

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Photoinduced Changes in Electrical Potentials and H+ Activities of the Chloroplast, Cytoplasm, and Vacuole of Phaeoceros laevis

Cited by 36 publications

References 11 publications

Effects of Environmental pH on the Internal pH of Chlorella pyrenoidosa, Scenedesmus quadricauda, and Euglena mutabilis

Effects of Environmental pH on the Internal pH of Chlorella pyrenoidosa, Scenedesmus quadricauda, and Euglena mutabilis

Effect of light upon membrane potential, conductance, and ion fluxes inRiccia fluitans

Electrical Properties of the Plasmalemma and Tonoplast in Valonia ventricosa

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