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1.
Potassium fluxes and the effect of phenol and bronopol on deplasmolysis of Pseudomonas aeruginosa were followed in sucrose and glycerol plasmolysing systems.
In sucrose, K+ uptake related to the solute concentration. Proline increased the rate and overall K+ uptake, the latter by a factor of three. It was concluded that there was no rigid maximum in the accumulation of intracellular K+ as long as intracellular neutrality in electrical charges was maintained.
In glycerol, K+ uptake was parallel with glycerol penetration. The process was reversed, however, on equilibration of glycerol. This suggested that glycerol inhibited K+ retention against a concentration gradient rather than that K+ was excluded as a consequence of the osmotic established steady state. This view was enforced by the fact that the reversal of K+ uptake occurred in 20 and 30% glycerol but not in 10%.
Phenol and bronopol did not affect deplasmolysis in glycerol significantly, although some effect on K+ uptake and glycerol permeability could be seen. In the sucrose system, phenol acted according to its mode of action generally accepted, i.e. inhibiting deplasmolysis at low and allowing solute penetration at higher concentrations, whereas very high concentrations caused coagulation of the cytoplasm. Bronopol inhibited deplasmolysis, except at very low concentrations. Proline did not prevent the inhibition of deplasmolysis in either of the solute systems, except at the very low bronopol concentrations where the deplasmolysis rate only was affected. 相似文献
In sucrose, K
In glycerol, K
Phenol and bronopol did not affect deplasmolysis in glycerol significantly, although some effect on K
2.
Terence M. Murphy 《Physiologia plantarum》1988,74(3):537-543
A low fluence of ultraviolet radiation (UV) causes cultured cells of Rosa damascena Mill cv. Gloire de Guilan to lose intracellular K+ . This effect required the presence of Ca2+ in the medium. A reduction in the concentration of free Ca2+ to 10−5 M with ethyleneglycol-bis-(β-aminoethyl-ether)-N.N.N',N'-tetraacetic acid (EGTA) buffer inhibited the UV-stimulated efflux; this was correlated with a discharge of the membrane potential and a stimulation of the leakage of K+ from unirradiated cells. All the same effects were seen with La3+ at 0.2 m M. At 0.02 m M La3+ , the UV-stimulated efflux of K+ was blocked without concomitant effects on the membrane potential or K+ efflux from control cells. It is suggested that removal of Ca2+ blocks or masks the UV-induced leakage of K+ by destabilizing the plasma membrane. In addition, La3+ may specifically inhibit the UV-stimulated opening of K+ or anion channels. 相似文献
3.
Effects of salinity and replacement of K+ by Na+ on lipid composition in two sugar beet inbred lines
The effects of NaCl and replacement of K+ by Na+ on the lipid composition of the two sugar beet inbred lines FIA and ADA were studied (a) with increasing additions of NaCl to the basal medium, and (b) with increasing replacement of K+ by Na+ at the same total concentration as in the basal medium. Direct relations were noted between NaCl concentration of the nutrient solution and the phospholipid concentration in the roots of FIA, the genotype characterized by a low K+ /Na+ ratio, as well as between NaCl in the medium and the phospholipid concentration in the shoots of ADA, the genotype with a high K + /Na + ratio. The sulfolipid level in the roots of FIA was maintained at higher NaCl concentrations, while it was decreased in ADA. The glycolipid concentration in the shoots of ADA and the degree of unsaturation of the fatty acids of the total lipid fraction were decreased by salinity, indicating reduced biosynthesis of chloroplast glycolipids and/or accelerated oxidation of these lipids in the presence of NaCl.
In the Na+ for K+ replacement experiment a low content of K+ in the medium resulted in decreased levels of total lipids, phospholipids and sulfolipid in the roots of both genotypes, which did not relate to root growth. K+ -leakage from the roots at low K+ -level in the medium may be reduced by the increase in saturation of the lipids. In the shoots of ADA increased levels of total lipids, phospholipids and Sulfolipid were noted at a low K+ -concentration of the nutrient solution. 相似文献
In the Na
4.
Sune Pettersson 《Physiologia plantarum》1981,52(4):431-436
Passive fluxes of K+ (86 Rb) into roots of sunflower ( Helianthus annuus L. cv. Uniflorus) were determined at low K+ concentration (0.1 and 1.0 mM K+ ) in the ambient solution. Metabolic uptake of K+ was inhibited by 10−4 M 2,4-dinitrophenol (DNP). K+ (86 Rb) fluxes were studied both continuously and by time differentiation of uptake. In high K+ roots passive uptake was directly proportional to the K+ concentration of the uptake solution, indicating free diffusion. This assumption was supported by the fact that passive Rb+ uptake was not affected by high K+ concentrations. In low K+ roots the passive uptake of K+ was higher than in high K+ roots. The increase was possibly due to carrier-mediated K+ transport. As K+ effluxes were quantitatively similar to influxes, it is suggested that passive K+ fluxes represent exchange diffusion without relation to net K+ transport. 相似文献
5.
Abstract Washed cells of Rhodopseudomonas sphaeroides forma sp. denitrificans , grown under photodenitrifying conditions, exhibited K+ uptake dependent on the transmembrane proton gradient (Δ pH). These cells also acidified the suspension medium in response to K+ pulses both aerobically and anaerobically in light and in the dark. The results indicate that the photodenitrifier has a reversible K+ /H+ exchange activity which reflects its role in regulating the intracellular K+ concentration, as well as intracellular pH. The acidification of the external medium resulting from K+ pulses was inhibited by carbonyl cyanide- m -chlorophenylhydrazone (CCCP) indicating that the antiporter is energy-dependent. Addition of KCl to washed cells depolarized the membrane potential (Δψ) with a concomitant increase in ΔpH, indicating that the K+ /H+ antiporter was electrogenic. 相似文献
6.
Low-K+ , high-Na+ cells of strain RL21a of Neurospora crassa , in steady state with 25 m M Na+ , were used to study K+ /Na+ exchanges in the presence or absence of Ca2+ and Mg2+ . In the presence of Ca2+ and Mg2+ , a low concentration of K+ (0.3 m M ) triggered a rapid exchange, but in the absence of the divalents, a high K+ concentration (30 m M ) was required to initiate the exchange at a rapid rate. In the absence of Ca2+ and Mg2+ , K+ uptake did not occur at low K+ concentration, internal K+ did not regulate Na+ influx in the presence of external K+ , and the efflux of Na+ proceeded at maximum activity at very low-K+ contents. 相似文献
7.
The effects of K+ concentration, light intensity and CO2 levels on the volume of Commelina communis L. guard cell protoplasts were studied. Two degrees of swelling response were observed, both dependent on an external supply of K+ , but not necessarily on the supply of a permeant anion. The presence of K+ itself, independent of light or CO2 level, stimulated swelling at a relatively slow rate. When K+ , light and low CO2 conditions were supplied together, the swelling was relatively rapid and of high magnitude. The rapid swelling was specific for K+ and Rb+ giving a half maximal effect after 2 h at a KCl concentration of about 18 mmol m−3 . The addition of CaCl2 at 1 mol m−3 inhibited K+ -dependent swelling under all conditions tested. The response to light and low CO2 levels by Commelina guard cell protoplasts is thought to reflect a high degree of physiological integrity. 相似文献
8.
Irradiation of cultured rose ( Rosa damascena Mill. cv. Gloire de Guilan) cells with ultraviolet light caused of loss of K+ , which occurred with sigmoid kinetics. The kinetics of loss of K+ were not changed when the extracellular concentration of K+ was held constant during the period of efflux. Furthermore, the rate of loss of K+ was approximately the same even though the K+ concentration in the medium was increased from 0.1 to 10 m M . The kinetics of uptake of the lipophilic methyltriphenylphosphonium cation, an indicator of the plasma membrane potential, were linear throughout the period of K+ efflux, suggesting that the starting and stopping of K+ efflux do not reflect a passive response to changes in the membrane potential of the cells. The results are interpreted in terms of activation and inactivation of an efflux channel or pump for K+ . 相似文献
9.
Salinity tolerance of Kosteletzkya virginica. II. Root growth, lipid content, ion and water relations 总被引:1,自引:0,他引:1
Abstract. Kosteletzkya virginica (L.) Presl., a dicot halophyte native to brackish tidal marshes, was grown on nutrient solution containing 0. 85, 170 or 255 mol m 3 NaCl, and the effects of external salinity on root growth, ion and water levels, and lipid content were examined in successive harvests. Root growth paralleled shoot growth trends, with some enhancement observed at 85 mol m 3 NaCl and a reduction noted at the higher salinities. Root Na+ content increased with increasing external NaCl, but remained constant with time for each treatment. K+ content, although lower in salt-grown plants after 14 d salinization, subsequently increased to levels comparable to unsalinized plants. A strong K+ affinity was reflected in the increased K+ /Na+ selectivity of salt-grown plants and by their low Na+ /K+ ratios. Cl levels rose in salinized plants and values were double or more those for Na+ , indicating the possibility of a sodium-excluding mechanism in roots. Root phospholipids and sterols, principal membrane constituents, were maintained or elevated and the free sterol/phospholipids ratio increased in salinized K. virginica plants, suggesting retention of overall membrane structure and decreased permeability. This response, considered in light of root calcium maintenance and high potassium levels, suggests that salinity-induced changes in membrane lipid composition may be important in preventing K+ leakage from cells. 相似文献
10.
Salinity tolerance of Kosteletzkya virginica. I. Shoot growth, ion and water relations 总被引:5,自引:2,他引:3
Abstract. Kosteletzkya virginica (L.) Presl., a dicotyledonous halophyte native to brackish tidal marshes, was grown on nutrient solution containing 0. 85, 170 or 255 mol m-3 NaCl, and the effects of external salinity on shoot growth and ion content of individual leaves were studied in successive harvests. Growth was stimulated by 85 mol m-3 NaCl and was progressively reduced at the two higher salinities. Growth suppression at high salinity resulted principally from decreased leaf production and area, not from accelerated leaf death. As is characteristic of halophytic dicots. K. virginica accumulated inorganic ions in its leaves, particularly Na+ and K+ . However, the Na+ concentration of individual leaves did not increase with time, but remained constant or even declined, seeming to be well-coordinated with changes in water content. A striking feature of the ion composition of salinized plants was the development of a dramatic gradient in sodium content, with Na+ partitioned away from the most actively growing leaves. Salt-treated plants exhibited a strong potassium affinity, with foliar K+ levels higher in salinized plants than unsalinized plants after an initial decrease. These results suggest that selective uptake and transport, foliar compartmentation of Na+ and K+ in opposite directions along the shoot axis, and the regulation of leaf salt loads over time to prevent build-up of toxic concentrations are whole-plant features which enable K. virginica to establish favourable K+ -Na+ relations under saline conditions. 相似文献
11.
Potassium ion channels in the plasmalemma 总被引:2,自引:0,他引:2
Friedrich-Wilhelm Bentrup 《Physiologia plantarum》1990,79(4):705-711
The potassium ion is an indispensible cytosolic component of living cells and a key osmolyte of plant cells, crossing the plasmalemma to drive physiological processes like cell growth and motor cell activity. K+ transport across the plasmalemma may be passive through channels, driven by the electrochemical gradient, K+ equilibrium potential (EK ) – membrane potential (Vm ), or secondary active by coupling through a carrier to the inward driving force of H+ or Na+ . Known K+ channels are permeable to monovalent cations, a permeability order being K+ > Rb+ > NH4 + > Na+ ≥ Li+ > Cs+ . The macroscopic K+ currents across a cell or protoplast surface commonly show rectification, i.e. a Vm -dependent conductance which in turn, may be controlled by the cytosolic activity of Ca2+ , of K+ , of H+ , or by the K+ driving force. Analysis by the patch clamp technique reveals that plant K+ channels are similar to animal channels in their single channel conductance (4 to 100 pS), but different in that a given channel population slowly activates and may not inactivate at all. Single-channel kinetics reveal a broad range of open times (ms to s) and closed times (up to 100 s). Further progress in elucidating plant K+ channels will critically depend on molecular cloning, and the availability of channel-specific (phyto)toxins. 相似文献
12.
Manuel Diaz de la Guardia José M. Fournier Manuel Benlloch 《Physiologia plantarum》1985,63(2):176-180
Young sunflower plants ( Helianthus annuus L. cv. Halcón), grown in nutrient solution at two K+ levels (0.25 and 2.5 m M ) were used to study the effect of K+ content in the root on uptake and transport of K+ to the exuding stream of decapitated plants. Roots of plants grown in low K+ gave higher exudation flux, higher K+ concentration in exudate and higher K+ flux than high K+ roots. After 6 h of uptake the K+ flux in low K+ roots was about three times that in high K+ roots. When the roots were kept in a nutrient solution in which Rb+ replaced K+ , low K+ roots exuded much more Rb+ than K+ after the first 2 h, whereas high K+ roots exuded about similar amounts of K+ and Rb+ . In intact plants grown at three different K+ levels (0.1, 1.0 and 10.0 m M ), there was an inverse relationship between the K+ level in the nutrient solution and the Rb+ accumulated in the roots or transported to the shoot. The results suggest that the transport of ions from xylem parenchyma to stele apoplast may be controlled by ions coming down from the shoot in sieve tubes. 相似文献
13.
The effect of phytochrome on K+ transport in guard cells of Commelina communis L. was studied following stomatal movement and using the K+ −channel blockers tetraethylammonium (TEA), Cs+ and quinidine. TEA and quinidine prevented stomatal opening and closure in red light, but not when it was supplemented with far-red. This indicates that channels that can be blocked by TEA and quinidine are regulated by phytochrome. Evidence for a phytochrome effect on K+ leakage through other membranal compartments was also found. These phytochrome effects are modified by temperature. Elevated temperature decreases the involvement of channels and increases K+ transport through other membrane compartments, while low temperature causes channel opening and diminishes K+ leakage. The interaction between phytochrome effects and those of temperature is discussed. 相似文献
14.
SUMMARY 1. Unialgal cultures of three species common in the freshwater phytoplankton were used to test limitation of specific growth rate and final yield in defined media of low K+ concentration (range <0.3–6 μmol L−1 or mmol m−3 ).
2. Growth rate of the diatom Asterionella formosa was independent of K+ concentration above 0.7 μmol L−1 . Final yield was dependent on initial concentration when accompanied by K+ depletion below this concentration, but not by lesser depletion with more residual K+ . Analyses of particulate K in the biomass indicated a mean final cell content of 2.8 μmol K 10−8 cells, approximately 1.0% of the organic dry weight.
3. Less detailed work with the diatom Diatoma elongatum showed no dependence of growth rate or final yield upon the initial K+ concentration in the range 0.8–3.2 μmol L−1 . The phytoflagellate Plagioselmis nannoplanctica suffered net mortality in the lowest concentration tested, 0.8 μmol L−1 .
4. Comparison with the range of K+ concentration in natural fresh waters, including a depletion induced by an aquatic macrophyte, suggests that K+ is unlikely to limit growth of phytoplankton. Nevertheless, there can be correlation of K+ with lake trophy. 相似文献
2. Growth rate of the diatom Asterionella formosa was independent of K
3. Less detailed work with the diatom Diatoma elongatum showed no dependence of growth rate or final yield upon the initial K
4. Comparison with the range of K
15.
Translocation of labeled potassium (K+ ) from the root to the ear and its distribution within the culm during 4, 8 and 12 h of uptake was studied in intact wheat plants ( Triticum aestivum L. cv. Kolibri) 3 and 5 weeks after anthesis at 0.5 and 5.0 m M K+ concentration in the uptake solution. Uptake of labeled K+ into the shoot was proportional to the K+ concentration applied. After 4 h of uptake about 2% and after 12 h about 7% of labeled K+ applied to the roots were taken up into the shoot at both K+ concentrations. After 12 h of uptake only 6% of the total label in the culm had reached the ear, while about 40% of the label was found in the upper three internodes. In spite of an increasing concentration of labeled K+ during 12 h in the uppermost internode (peduncle), translocation of K+ into the rachis was low. The low and uniform K+ content found generally in grain dry weight seems therefore to be due to a controlled K+ supply to the ear. 相似文献
16.
Potassium Movements in Relation to Synaptosomal Morphology 总被引:6,自引:6,他引:0
17.
The effects of external K+ , H+ and Ca2+ concentrations on the intracellular K+ concentration, [K+ ]i, and the K+ -ATPase activity in 2-day-old mung bean roots [ Vigna mungo (L.) Hepper] were investigated. [K+ ]i, in mung bean roots was markedly decreased by external K+ or H+ stress and did not recover the initial value even after the stress was removed. This decrease in [K+ ]i, gradually disappeared with the addition of (Ca2+ . Ca2+ may offset the harmful effects of ion stress. Ca2+ seems to have two effects on K+ transport; control of K+ permeability and activation of K+ uptake, although K+ -ATPase activity was inhibited by Ca2+ concentrations higher than 10–4 M. We suggest that Ca2+ activates K+ uptake indirectly through the acidification of the cytoplasm. 相似文献
18.
Sano T Kutsuna N Becker D Hedrich R Hasezawa S 《The Plant journal : for cell and molecular biology》2009,57(1):55-64
Potassium ions (K+ ) are required for plant growth and development, including cell division and cell elongation/expansion, which are mediated by the K+ transport system. In this study, we investigated the role of K+ in cell division using tobacco BY-2 protoplast cultures. Gene expression analysis revealed induction of the Shaker -like outward K+ channel gene, NTORK1 , under cell-division conditions, whereas the inward K+ channel genes NKT1 and NtKC1 were induced under both cell-elongation and cell-division conditions. Repression of NTORK1 gene expression by expression of its antisense construct repressed cell division but accelerated cell elongation even under conditions promoting cell division. A decrease in the K+ content of cells and cellular osmotic pressure in dividing cells suggested that an increase in cell osmotic pressure by K+ uptake is not required for cell division. In contrast, K+ depletion, which reduced cell-division activity, decreased cytoplasmic pH as monitored using a fluorescent pH indicator, SNARF-1. Application of K+ or the cytoplasmic alkalizing reagent (NH4 )2 SO4 increased cytoplasmic pH and suppressed the reduction in cell-division activity. These results suggest that the K+ taken up into cells is used to regulate cytoplasmic pH during cell division. 相似文献
19.
The relationship between the inhibiting effect of Ca2+ and of low turgor pressure on K+ release from fresh-cut discs of carrot ( Daucus carota var. Nantes) storage tissue was studied. A range of Ca2+ concentrations in the tissue was obtained by adding 0.5 m M EDTA or CaSO4 at different concentrations to the medium. Calcium inhibited K+ release in fully turgid cells (2.5 μmol K+ g−1 h−1 in 0.5 m M EDTA vs 0.4 μmol K+ g−1 h−1 in 10 m M CaSO4 ). Less turgid cells, obtained by equilibration with 0.2 M mannitol, released K+ at only 30% of the rate of the turgid cells, yet the pattern of K+ release as a function of Ca2+ level was similar in both turgid and non-turgid cells. Removal of calcium by EDTA occasionally injured cell membranes in the fully turgid discs but never in the less turgid ones. In view of the additive effect of Ca2+ and low turgor on K+ release regardless of the treatment order, it is suggested that the two factors exert their effect on membrane permeability independently of each other. 相似文献
20.
Abstract. Xanthoxylin is a cytotoxic and fungicidal compound with the characteristics of a typical phytoalexin. At a concentration of 0.3 mol m−3 it inhibits K+ -dependent acid extrusion and K+ net uptake (or uptake of equivalent alkaline cations such as Rb+ and CS+ ) by up to about 80% and hyperpolarizes by about 20% the membrane electrical potential. Its inhibition of the acid extrusion does not depend on altered ion exchange involving the anions in the media, a reduction of the metabolic energy available, or detectable changes in the permeability of the cell membrane to H+ ions. The drop in K+ net uptake depends on a decrease in the influx of K+ into the cell. In functional terms, xanthoxylin is an inhibitor of the K+ permeation mechanism and does not appear to interact with the mechanisms creating the electrochemical energy gradient. 相似文献