[14C]Carbon-dioxide fixation by isolated leaf epidermes with stomata closed or open

Following small hypo-osmotic shocks, ion concentrations (Na⁺, K⁺, Cl^-) in Platymonas subcordiformis decreased; this was due mainly to an increase of cell volume. With larger hypo-osmotic stresses, the decrease of ion concentration continued and, additionally, extrusion of mannitol was observed. The ion and mannitol concentrations were not regained after 240 min. In contrast, following hyperosmotic shocks, the ion concentrations increased transitorily during the first 20–40 min. The same was true for K⁺ following small hyperosmotic stresses and for Na⁺ and — partially — Cl^- with larger shocks. Large hyperosmotic stresses caused permanent accumulation of mannitol, which levelled off after 60–80 min. Thus the transient increase of ions bridged the concentration gap until mannitol was accumulated to a high enough concentration to account for the osmotic adaptation of Platymonas, together with a basal level of the ions K⁺, Na⁺, Cl^-.Abbreviations PS photosynthesis - Resp respiration     

Changes in haemolymph ion concentrations of Astacus astacus L. and Pacifastacus leniusculus (Dana) after exposure to low pH and aluminium

During exposure to soft water, acidified to pH 4.0, the haemolymph concentrations of Na⁺, K⁺, and Cl^– decreased whereas the Ca²⁺ concentration fluctuated in Astacus astacus. The haemocyte content of K⁺ decreased from 9% to 2% of the total haemolymph K⁺ content after exposure to pH 3.7 for 3 days. Within 14 days, 250 µg Al³⁺ l^–1, as Al₂(SO₄)₃ at pH 5.0, reduced the haemolymph Na⁺ content in Astacus astacus and Pacifastacus leniusculus, however, the effects were less pronounced than earlier reported for fish. Disturbed ion regulation, mainly depending on low pH, is thought to contribute to the absence of these species in acid waters.     

Effects of haemolymph free cations on blowfly taste receptor responses

Ionic composition of the haemolymph and electrophysiological responses of tarsal taste hairs were determined for individual flies of the species Calliphora vicina, in order to test the hypothesis that electrophysiological response values of individual flies are correlated with the ionic composition. Instead of flame photometry we used isotachophoresis to determine the ionic composition; only non-bound ions contribute to the result. Because of this we found lower concentration values than those reported so far. There was a strong correlation between the concentrations of the cations Na⁺, K⁺ and Mg²⁺, while Ca²⁺ was not related with any other cation. A significant correlation was shown to exist between the response of taste cells and the Na⁺, K⁺ and Ca²⁺ content in the haemolymph. These correlations explain, at least partly, the systematic differences in taste cell responses between flies, as reflected in interindividual variability.     

Effects of Inhibitors of Protein and Nucleic Acid Synthesis on the Development of Ion Uptake Mechanisms in Beetroot Slices (Beta vulgaris)

Mechanisms for the uptake of K⁺, Na⁺ and Cl^- develop sequentially in thin slices of beetroot tissue washed under aerobic conditions. Actinomycin D inhibited or prevented the development of K⁺, Na⁺ and Cl^- uptake mechanisms when added to freshly cut slices, but had no effect on net ion uptake when added after the development of the ion uptake mechanisms. The use of puromycin as a specific inhibitor of protein synthesis was unsatisfactory as it caused leakage of pigments and excessive loss of ions from the disks. Cycloheximide prevented the development of ion uptake mechanisms when added at the start of the experiment, but when added after the development of ion uptake mechanisms its inhibitory effect did not become apparent until after a certain time interval which varied from 3 hours for Cl^- to 25 hours for K⁺ uptake in the same experiment. p-Fluorophenylalanine caused an appreciable shortening of the time required for the development of Na⁺ and K⁺ uptake capabilities, while it completely prevented the development of a Cl^- uptake mechanism. p-Fluorophenylalanine-induced early uptake of Na⁺ and K⁺, however, was followed by periods of net leakage of these ions. It is suggested that the development of ion uptake mechanisms depends on the production of m-RNA, which appears to be relatively stable after its synthesis. The synthesis and decay characteristics of specific proteins required for the ion uptake mechanisms appear to differ for each ion species.     

Quantitative ion localization within Suaeda maritima leaf mesophyll cells

Grown under saline conditions, Suaeda maritima accumulates Na⁺ and Cl^- into its leaves, where individual mesophyll cells behave differently in their compartmentation of these ions. Measurements of ion concentrations within selected subcellular compartments show that freeze-substitution with dry sectioning is a valuable preparative technique for analytical electron microscopy of highly vacuolate plant material. Using this approach, absolute estimates were made of Na⁺, K⁺ and Cl^- concentrations in the cytoplasm, cell walls, chloroplasts and vacuoles of leaf mesophyll cells.Abbreviation TAEM transmission analytical electron microscopy     

Ion composition of unicellular marine and fresh-water algae,with special reference to Platymonas subcordiformis cultivated in media with different osmotic strengths

Summary Ion compositions (K⁺, Na⁺ Mg²⁺, Ca²⁺, Cl^-, phosphate) of the euryhaline algae, Platymonas subcordiformis, Chlorella salina, grown in media with a salinity range from 0.1 to 0.6 M NaCl and of the fresh-water algae, Ankistrodesmus braunii and Scenedesmus obliquus, were compared. Enhancement of ion concentrations with increasing salinity in Platymonas was attributed largely to decreasing cell volume. In both the euryhaline algae, Na⁺ and — partially — Cl^- content per cell increased significantly with rising salinity. The contents per cell of the other ions were not affected. Considering the relevance of ions and mannitol (Platymonas) and proline (Chlorella) as osmotically active particles, it was found that the ions alone maintained osmotic balance with low external salinity. With increasing salinity the organic compounds contributed up to 20–30% of the cellular solute potential. The main cation, K⁺, was the main contributor to the osmotic balance; the accumulation of organic compounds as well as of Na⁺ and Cl^- contributes further to the ability of the algae to adapt to high salinity. The results confirm the hypothesis of low Cl^- concentrations in nonvacuolate cells in comparison to vacuolate cells.     

The role of ion regulation in the control of the distribution of Gammarus tigrinus (Sexton) in salt-polluted rivers

Fluctuating salinities at different sites on the German salt-polluted rivers Werra and Weser were compared with extracellular ion levels of specimens of Gammarus tigrinus (Sexton; Amphipoda, Crustacea), collected at the same sites. G. tigrinus regulated haemolymph concentrations of inorganic anions (Cl⁻, SO²⁻ ₄, PO³⁻ ₄) and cations (Na⁺, K⁺, Mg²⁺, Ca²⁺) during fluctuations of salt pollution in the upper Weser. This capacity to regulate varying levels of salt pollution in the upper Weser, correlated well with the distribution of the brackish amphipods in this river ecosystem. G. tigrinus tolerated periods of Na⁺ and Cl⁻ stress (>380 mmol l⁻¹) without compensating these maxima by regulating extracellular Na⁺ and Cl⁻. However, during such bursts of Na⁺ and Cl⁻ stress in Werra and Weser, the ability to regulate extracellular [K⁺] at river water K⁺ stress of ≥6.0 mmol l⁻¹ may explain why this brackish species has been more successful in these rivers than its competitors like Gammarus pulex. The present investigation demonstrates that the water salinity affects the [NO⁻ ₃] in the haemolymph of G. tigrinus. With increasing hypo-osmotic stress the animals accumulate increasing amounts of NO⁻ ₃. A simultaneous increase in stream water [NO⁻ ₃] causes an additional accumulation of NO⁻ ₃ in the haemolymph. The high extent of accumulation indicates that active ion transport systems may be involved. The accumulation of NO⁻ ₃ in the haemolymph has low physiological consequences to G. tigrinus, but when hypo-osmotically stressed under anoxic conditions, nitrite formed by the reduction of nitrate may have an adverse affect on the metabolism of G. tigrinus. Accepted: 4 October 1999     

Osmotic adjustment in triticales grown in presence of NaCl

Growth and Na⁺, K⁺, Cl^-, proteins, sugars and proline concentrations were measured in three triticale genotypes M2A, DF99 and Asseret grown on nutrient solution with or without 75 mM NaCl. In saline conditions, leaf area of the three triticales was reduced by 50 % and dry to fresh mass ratio increased. Total protein concentration was diminished by 10 %. K⁺ concentration decreased whereas Na⁺ and Cl^- accumulated in roots and shoots of salt-stressed plants. This ion accumulation was greater in roots of Asseret than in roots of the other triticales. Soluble sugar concentration increased in M2A and Asseret and decreased in DF99. Proline concentration increased in M2A and DF99 and decreased in Asseret. Osmotic adjustment was essentially realized by Na⁺ and Cl^- uptake. Non-reducing sugars and proline contributed too, but to a lesser extent. This revised version was published online in July 2006 with corrections to the Cover Date.     

The effects of salinity on ion concentrations within the root cells of Zea mays L.

Zea mays is a salt-sensitive crop species which in saline (100 mol m^-3 NaCl) conditions suffers considerable growth reduction correlated with elevated Na⁺ and Cl^- concentration within the leaves. To increase understanding of the regulation of ion uptake and transport by the roots in saline conditions, ion concentrations within individual root cortical cells were determined by X-ray microanalysis. There was variation in Na⁺, K⁺ and Cl^- distributions among individual cells, which could not be correlated with their spatial position in the roots. Generally, however, in response to saline growth conditions (100 mol m³ NaCl) Na⁺ and Cl^- were mostly localized in the vacuoles, although their concentrations were also sometimes increased in the cytoplasm and cell walls. The concentration of K⁺ in the cytoplasm was usually maintained at a level (mean 79 mol m^-3) compatible with the biochemical functions ascribed to this ion.Abbreviation (T)AEM (Transmission) analytical electron microscopy     

Effects of starvation and dehydration on ionic balance in Schistocerca gregaria

This study describes the effects that prolonged dehydration has on ionic balance in Schistocerca gregaria. When adult locusts are dehydrated for 7 days the body weight reduces by 10–20% and the haemolymph volume by 35–50%, but haemolymph concentrations of Na⁺, K⁺ and Cl⁻ change only slightly. On dehydration Na⁺ and Cl⁻ are removed from the haemolymph; 25% of the removed ions is excreted and 75% is evenly distributed in the body of the locust. The amount of potassium excreted always exceeds that removed from the haemolymph. Mature adults control more effectively than young ones the haemolymph ionic composition during dehydration, but young adults show a smaller reduction in haemolymph volume. In the normal state of hydration, 76% of the total body Na⁺ and 56% of the total body Cl⁻ is present in the haemolymph. These fall to 62 and 42% respectively on dehydration and increase to 77 and 50% on rehydration.     

ROLE OF INORGANIC IONS IN CONTROLLING SEDIMENTATION RATE OF A MARINE CENTRIC DIATOM DITYLUM BRIGHTWELLI1,2

The settling rates and intracellular levels of K⁺, Na⁺, Cl^-, Mg²⁺ and Ca²⁺ were measured in Ditylum bright-welli (West) Grunow, grown axenically in an enriched seawater medium at 20 C at 4,000 lx on an 8:16 LD schedule. Cells at the end of the dark period have high Na⁺ (118 mM), low K⁺ (64 mM) and low Cl^- (117 mM) relative to levels at the end of the light period when K⁺ (126 mM) and Cl^- (154 mM) are high and Na⁺ (101 mM) is low. There is no significant change in Mg²⁺ (16–18 mM) or Ca²⁺ (3–4 mM) with time. The net result of the ion changes during the light period is to increase cell density by about 3.4 mg ml^-1. This change can account for the increase in settling rate of ca. 0.3 day^-1 during the same interval. The density of the cell contents, calculated from observed ion concentrations, is 15–18 mg.ml^-1 less than that of the seawater medium. The ion and settling rate changes are light-dependent and do not persist in the dark or under constant light (ca. 850 lx), but cells do exhibit a free-running circadian rhythm in cell division under continuous dim illumination. The cell vacuole expands during the light period and contracts during the dark, apparently in response to the net ion fluxes. D. brightwelli appears to regulate its density by active ion selectivity accompanied by trans-vacuolar water movement.     

Microbodies and glyoxylate-cycle enzyme activities in filamentous fungi

Summary From compartmental analysis of radioisotope elution measurements, concentrations and fluxes of K⁺, Na⁺ and Cl^- were estimated for cortical cells in root segments of onion, Allium cepa L., relative to a complete nutrient solution. The transported fraction of the total efflux was estimated separately. With the Ussing-Teorell flux ratio equation as the criterion, it was concluded that all three ions were actively accumulated from the outside medium into the cytoplasm and that only Na⁺ was actively accumulated into the vacuole. K⁺ and Cl^- moved passively, in both directions across the tonoplast. Failure to account for leakage from the stele via the segment cut ends resulted in an over-estimate of exchange across the tonoplast but did not alter the conclusions qualitatively. The consequences of changing the assumed value of the tonoplast electrical potential (from 0 to+10- mV), and the effects of different experimental procedures, were also assessed, and found not to affect the main conclusions significantly. Separate measurement of ions leaking from the segment ends revealed that Na⁺ was transported almost exclusively in an acropetal direction in the stele. Cl^- appeared at both ends of the segments in similar amounts and K⁺ was transported mainly in the basipetal direction. The implications of these findings for the mechanism and site of ion selectivity are discussed.     

Effect of salinity on Na+, K+ and Cl- content in different organs of chickpea and the basis of ion expression

One-month-old plants of two chickpea (Cicer arietinum L.) cultivars were exposed to salinity of 4 and 8 dS m ^-1 in pots in a greenhouse. The cultivar BG 312 performed better than Pusa 209 in terms of visible injury and dry mass accumulation. Tissue water content of the various plant organs was affected differently by salinity. Expression of Na⁺ and Cl ^- concentrations on a dry mass basis indicated retention of Na⁺ and Cl ^- by roots, thereby keeping the leaves free of ion accumulation, but their expression on a tissue water basis did not indicate Cl ^- retention and showed less Na ^- exclusion. Changes in the apparent exclusion mechanisms resulted from a higher water content in the roots than in the shoots. On a dry mass basis, roots appeared to retain K⁺, but on a tissue water basis stems appeared to act as a reservoir of K⁺; leaves and nodules received K⁺ preferentially. The exclusion mechanisms and their efficiency differ with cultivar and salinity. The expression of ion concentrations on a tissue water basis appears to be more useful then on a dry mass basis in studies of salinity tolerance.     

Inorganic ions in spermathecal fluid and their transport across the spermathecal membrane of the queen bee, Apis mellifera

Micropuncture and microanalytical methods were employed to investigate the rôle of the spermathecal epithelium of the honey queen-bee in providing the appropriate conditions for the prolonged storage of spermatozoa. It was found that the epithelium maintains large concentration gradients of inorganic ions, generates an electrical potential difference of 21 mV, lumen positive, and produces a pH difference of up to 2.4 pH units between spermathecal fluid (SF) and haemolymph (H). The $\text{SF}\text{H}$ concentration ratios for K⁺, Na⁺, Ca⁺⁺, Cl^?1, HPO₄^??, H₂PO₄^? and amino acids were 7.7; 0.5; 0.8; 0.4; 1.03; 0.004; 0.3, respectively. While the pH value of haemolymph was constant at 6.17, the pH of SF increased with age from 7.3 to 8.6 over the first 3 days. The calculated electrochemical potential differences suggest that the epithelium of the spermathecal wall secretes K⁺ (and possibly HCO₃^? or OH^?) actively into the lumen, but handles Na⁺ passively. This pattern conforms with the organization of ion transport in other insects.     

Effects of salinity on uptake and distribution of Na+, Cl- and K+ in two wheat cultivars

Plants of two wheat (Triticum aestivum L.) cultivars differing in salt tolerance were grown in sand with nutrient solutions. 35-d-old plants were subjected to 5 levels of salinity created by adding NaCl, CaCl₂ and Na₂SO₄. Growth reduction caused by salinity was accompanied by increased Na⁺ and Cl^- concentrations, Na⁺/K⁺ ratio, and decreased concentration of K⁺. The salt tolerant cv. Kharchia 65 showed better ionic regulation. Salinity up to 15.7 dS m^-1 induced increased uptake of Na⁺ and Cl^- but higher levels of salinity were not accompanied by further increase in uptake of these ions. Observed increases in Na⁺ and Cl^- concentrations at higher salinities seemed to be the consequence of reduction in growth. Uptake of K⁺ was decreased; more in salt sensitive cultivar. This was also accompanied by differences in its distribution.     

Relation between Ion Accumulation of Salt-Sensitive and Isolated Stable Salt-Tolerant Cell Lines of Citrus aurantium

Four selected NaCl-tolerant cell lines of Sour orange (Citrus aurantium) were compared with the nonselected cell line in their growth and internal ion content of Na⁺, K⁺, and Cl⁻ when exposed to increasing NaCl concentrations. No difference was found among the various NaCl-tolerant cell lines in Na⁺ and Cl⁻ uptake, and all these cell lines took up similar or even larger amounts of Na⁺ and Cl⁻ than the NaCl-sensitive cell line. Exposure of cells of NaCl-sensitive and NaCl-tolerant lines to equal external concentrations of NaCl, resulted in a greater loss of K⁺ from the NaCl-sensitive cell line. This observation leads to the conclusion that growth and ability to retain high levels of internal K⁺ are correlated. Exposure of the NaCl-tolerant cell lines to salts other than NaCl resulted in even greater tolerance to Na₂SO₄, but rather poor tolerance to K⁺ introduced as either K₂SO₄ or KCl; the latter has a stronger inhibitory effect. The NaCl-sensitive cell line proved to be more sensitive to replacement of Na⁺ by K⁺. Analyses of internal Na⁺, K⁺, and Cl⁻ concentrations failed to identify any particular internal ion concentration which could serve as a reliable marker for salt tolerance.     

Effects of antidiuretic hormone on cellular conductive pathways in mouse medullary thick ascending limbs of Henle: I. ADH increases transcellular conductance pathways

Summary This paper reports experiments designed to assess the relations between net salt absorption and transcellular routes for ion conductance in single mouse medullary thick ascending limbs of Henle microperfusedin vitro. The experimental data indicate that ADH significantly increased the transepithelial electrical conductance, and that this conductance increase could be rationalized in terms of transcellular conductance changes. A minimal estimate (G _c ^min ) of the transcellular conductance, estimated from Ba⁺⁺ blockade of apical membrane K⁺ channels, indicated thatG _c ^min was approximately 30–40% of the measured transepithelial conductance. In apical membranes, K⁺ was the major conductive species; and ADH increased the magnitude of a Ba⁺⁺-sensitive K⁺ conductance under conditions where net Cl^– absorption was nearly abolished. In basolateral membranes, ADH increased the magnitude of a Cl^– conductance; this ADH-dependent increase in basal Cl^– conductance depended on a simultaneous hormone-dependent increase in the rate of net Cl^– absorption. Cl^– removal from luminal solutions had no detectable effect onG _e , and net Cl^– absorption was reduced at luminal K⁺ concentrations less than 5mm; thus apical Cl^– entry may have been a Na⁺,K⁺,2Cl^– cotransport process having a negligible conductance. The net rate of K⁺ secretion was approximately 10% of the net rate of Cl^– absorption, while the chemical rate of net Cl^– absorption was virtually equal to the equivalent short-circuit current. Thus net Cl^– absorption was rheogenic; and approximately half of net Na⁺ absorption could be rationalized in terms of dissipative flux through the paracellular pathway. These findings, coupled with the observation that K⁺ was the principal conductive species in apical plasma membranes, support the view that the majority of K⁺ efflux from cell to lumen through the Ba⁺⁺-sensitive apical K⁺ conductance pathway was recycled into cells by Na⁺,K⁺,2Cl^– cotransport.     

The ionic relations of Porphyra purpurea(Roth) C.Ag. (Rhodophyta, Bangiales)

Abstract Radioisotope equilibration techniques have been used to determine the intracellular concentration of K⁺, Na⁺ and Cl_?, together with the unidirectional ion fluxes across the plasmalemma of Porphyra purpurea. Influx and efflux of ⁴²K⁺, ²⁴Na⁺ and ³⁶C1^? are biphasic, the rapid, initial uptake and loss of tracer from individual thalli being attributable to desorption from extracellular regions. Cellular fluxes are slower and monophasic, cells discriminating in favour of K⁺ and Cl^? and against Na⁺. A comparison between the equilibrium potential of individual ion species and the measured membrane potential demonstrates that there is an active component of K⁺ and Cl^? influx and Na⁺ efflux. ‘Active’ uptake and ‘passive’ loss of K⁺ and Cl^? are reduced when plants are kept in darkness, suggesting that a fraction of the transport of K⁺ and Cl^? may be due to ‘exchange diffusion’ (K⁺/K⁺ and Cl^?/Cl^?antiport).     

Calculations of K+, Na+, and Cl? fluxes across cell membrane with Na+/K+ pump, NKCC, NC cotransport and ionic channels with non-Goldman rectification in K+-channels: Normal and apoptotic cells

The balance of K⁺, Na⁺, and Cl⁻ fluxes across the cell membrane with the Na⁺/K⁺ pump, ion channels, and Na⁺K⁺2Cl⁻ (NKCC) and Na⁺-Cl⁻ (NC) cotransport was calculated to determine the mechanism of cell shrinkage in apoptosis. It is shown that all unidirectional K⁺, Na⁺, and Cl⁻ fluxes; the ion channel permeability; and the membrane potential can be found using the principle of the flux balance if the following experimental data are known: K⁺, Na⁺, and Cl⁻ concentrations in cell water; total Cl⁻ flux; total K⁺ influx; and the ouabain-inhibited pump component of the Rb⁺(K⁺) influx. The change in different ionic pathways during apoptosis was estimated by calculations based on the data reported in the preceded paper (Yurinskaya et al., 2010). It is found that cell shrinkage and the shift in ion balance in U937 cells induced to apoptosis with 1 μM staurosporine occur due to the coupling of reduced pump activity with a decrease in the integral permeability of Na⁺ channels, whereas K⁺ and Cl⁻ channel permeability remains almost unchanged. Calculations show that only a small part of the total fluxes of K⁺, Na⁺, and Cl⁻ account for the fluxes mediated by NKCC and NC cotransporters. Despite the importance of cotransport fluxes for maintaining the nonequilibrium steady-state distribution of Cl⁻, they cannot play a significant role in apoptotic cell shrinkage because of their minority and cannot be revealed by inhibitors.     

The relationship between sodium,potassium, and chloride in amphibian muscle

The Na,⁺ Cl^-, and K⁺ content of toad plasma and the sartorius muscle has been determined. Although the Na⁺ and Cl^- level of the muscles in the living animal varied greatly (0 to 38.0 m.eq. per kg., and 0 to 31.8 m.eq. per kg. respectively) the K⁺ level was subject to a smaller variation (76.5 to 136 m.eq. per kg.). There was a direct relationship between Na⁺ and Cl^-, which was independent of the K⁺ level. There is a closely related gain of Na⁺ and Cl^- when muscle is soaked in normal Ringer. These gains are not related to the K⁺ loss, frequently found on soaking. The relationship between the three ions was studied in a large series of 124 muscles in normal Ringer. As found in vivo, there was a correlation between Na⁺ and Cl.^- This correlation was independent of K⁺ content, except when this was abnormally low. Alteration of the external NaCl level produced concomitant changes in the internal levels of these ions. Alteration of the external KCl level produced an increase in internal Cl^- similar to that found with high NaCl solutions, but the amount of K⁺ entering the cell was approximately one-third of the external increase. Removal of K⁺ from the external solution did not result in a loss of K⁺ from the cell, although there was an adequate amount of Cl^- present to accompany it. The results cannot be reconciled with either a Donnan concept for the accumulation of K⁺, or a linked carrier system. A theory is proposed to account for the ionic differentiation within the cell. The K⁺ is assumed to be adsorbed onto an ordered intracellular phase. The normal metabolic functioning of the cell is necessary to maintain the specificity of the adsorption sites. There is another intracellular phase, which lacks the structural specificity for K⁺, and which contains Na⁺, Cl^-, and K⁺ in equilibrium with the external solution. The dimensions of the free intracellular phase will vary from cell to cell, but it will be smaller in the intact animal, and will increase on soaking in normal Ringer, until it is approximately one-third of the total cellular volume. The increase in this phase may be ascribed to a decrease in the energy available to maintain the ordered phase.