Ionic relations and the regulation of turgor pressure in the marine alga,Valonia macrophysa

Hastings, David F.; Gutknecht, John

doi:10.1007/bf01869700

Cited by 38 publications

(14 citation statements)

References 18 publications

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“…Ventricaria responds to hypertonic stress and decreased turgor with enhanced K + uptake. Flux measurements (Gutknecht, 1967;Hastings & Gutknecht, 1974;Hastings & Gutknecht, 1976;Steudle et al, 1977;Gutknecht et al, 1978) indicate that this is due to increased unidirectional (active) K + influx, which is minimal at normal turgor ( 0.15 MPa). This K + influx does not further decline when hypotonic stress is imposed, and turgor increases.…”

Section: Turgor Regulationmentioning

confidence: 99%

“…Hastings and Gutknecht (1976) Table 2 and Fig. 1b, Lewis & McCourt, 2004) and nuclear DNA data (Kapraun, 2005).…”

Section: Electrophysiologymentioning

confidence: 99%

“…The solutes responsible for turgor regulation are primarily K + and Cl ) ( Hastings & Gutknecht, 1976;Steudle et al, 1977). Na + is actively transported out of the cytoplasm at both membranes, but plays little part in adjusting turgor.…”

Section: Turgor Regulationmentioning

confidence: 99%

“…The experimenter can then control parameters when trying to understand the causes and significance of electrophysiological changes. Even turgor can be controlled in a perfused cell (Hastings & Gutknecht, 1974;Hastings & Gutknecht, 1976;Heidecker et al, 2003b). Advances in technology have enabled measurements on smaller cells using patch-clamp techniques, which require an intimate interaction between the membrane and the patch pipet, and consequently the removal of the cell wall.…”

Section: Introductionmentioning

confidence: 99%

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Electrophysiology of Turgor Regulation in Marine Siphonous Green Algae

2006

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Abstract. We review electrophysiological measures of turgor regulation in some siphonous green algae, primarily the giant-celled marine algae, Valonia, and Ventricaria, with particular comparison to the well studied charophyte algae Chara and Lamprothamnium. The siphonous green algae have a less negative plasma membrane potential, and are unlikely to have a proton-based chemiosmotic transport system, dominated by active electrogenic K + uptake. We also make note of the unusual cellular structure of the siphonous green algae. Hypertonic stress, due to increased external osmotic pressure, is accompanied by positive-going potential difference (PD), increase in conductance, and slow turgor-regulation. The relationship between these is not yet resolved, but may involve changes in K + conductance (G K ) or active K + transport at both membranes. Hypotonic turgor regulation, in response to decrease external osmotic pressure, is 3 times faster than hypertonic turgor regulation. It is accompanied by a negative-going PD, although conductance also increases. The conductance increase and the magnitude of the PD change are strongly correlated with the magnitude of hypotonic stress.

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Section: Turgor Regulationmentioning

confidence: 99%

“…Hastings and Gutknecht (1976) Table 2 and Fig. 1b, Lewis & McCourt, 2004) and nuclear DNA data (Kapraun, 2005).…”

Section: Electrophysiologymentioning

confidence: 99%

Section: Turgor Regulationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electrophysiology of Turgor Regulation in Marine Siphonous Green Algae

2006

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“…Both these effects are consistent with the operation of an electrogenic K+ influx pump in the tonoplast. Additional evidence for the K+ pump is the inhibition of both net K+ influx to the vacuole and E. by azide and cyanide (17). However, the possibility of an electrogenic pumping of H+ from the cytoplasm into the vacuole cannot be ruled out.…”

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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Essential nutritional ions show enrichment (K⁺, Mg²⁺) and depletion (NO₃⁻) in runoff water generated by biocrusts covering arid sand dunes under natural rain conditions

Kidron,

Xiao,

Starinsky

2024

Hydrological Processes

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The role of runoff in providing nutrients to runon loci in deserts was not extensively explored. Here we report 2 years of measurements of the chemical composition of rain and runoff (three events for each year, which correspond to the long‐term runoff events) in plots that were constructed over four biocrust types in the Negev Desert, Israel. The enrichment ratios showed high variability, being high for K+ (3.7), moderately high for NH4+ (1.6) and slightly high for Mg2+ and SO42− (1.2). It was low for Cl− and NO3− (0.5), moderately lower for Ca2+ (0.7) and slightly lower for Na+ and HCO3− (0.8). When examined per rain event, significant higher concentrations were found for K+ and Mg2+ while NO3− exhibited significantly lower concentration. The high enrichment of K+ and the enrichment of Mg2+ may point to a biogenic origin. While K+ enrichment is suggested to result from K+ excretion by the cyanobacteria, bacteria, and possibly by the mosses following cell wetting and the K+ role in cell osmoregulation, decomposition and erosion of the chlorophyll pigment may result in Mg2+ release. On the other hand, the data point out that despite the crust capability to fix nitrogen and thus to provide its own needs for nitrogen, NO3− was depleted from the runoff water, a phenomena that may be explained by the crust preference to utilise available low‐cost nitrogen provided by rain. Due to runoff accumulation at small depressions within the interdune and at the dune‐interdune interface, runoff may contribute additional amount of nutrients to these habitats. For the dune‐interdune interface it may account for an addition of 273.8% and 35.3% of the total potassium and nitrogen, respectively. The addition of water and nutrients may have important contribution to the growth of the moss‐dominated biocrusts and the shrubs at the dune‐interdune interface, being responsible for the formation of ‘mantles and islands of fertility’ at the dune‐interdune interface. It also points to the possible role that biocrusts may play in agroforestry practices.

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Ionic relations and the regulation of turgor pressure in the marine alga,Valonia macrophysa

Cited by 38 publications

References 18 publications

Electrophysiology of Turgor Regulation in Marine Siphonous Green Algae

Electrophysiology of Turgor Regulation in Marine Siphonous Green Algae

Electrical Properties of the Plasmalemma and Tonoplast in Valonia ventricosa

Essential nutritional ions show enrichment (K⁺, Mg²⁺) and depletion (NO₃⁻) in runoff water generated by biocrusts covering arid sand dunes under natural rain conditions

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Ionic relations and the regulation of turgor pressure in the marine alga,Valonia macrophysa

Cited by 38 publications

References 18 publications

Electrophysiology of Turgor Regulation in Marine Siphonous Green Algae

Electrophysiology of Turgor Regulation in Marine Siphonous Green Algae

Electrical Properties of the Plasmalemma and Tonoplast in Valonia ventricosa

Essential nutritional ions show enrichment (K+, Mg2+) and depletion (NO3−) in runoff water generated by biocrusts covering arid sand dunes under natural rain conditions

Contact Info

Product

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About

Essential nutritional ions show enrichment (K⁺, Mg²⁺) and depletion (NO₃⁻) in runoff water generated by biocrusts covering arid sand dunes under natural rain conditions