The impact of acidification on diatoms and chemistry of Dutch moorland pools

Summary Moorland pools are shallow oligotrophic soft water lakes on poorly buffered sandy soils. Diatom assemblages of samples from 16 pools taken in 1920 and 1978 were compared by analysis of pH-spectra, diversity, dissimilarity and multivariate statistical techniques.The pH-spectra of pools in the southern (S) and central (C) part of the country indicate a fall in pH from 4.5–6.0 in the old samples to 3.7–4.6 in the recent ones. The pH-spectra of the northern pools (N) do not indicate a significant shift from the original pH (ca 4.5).The number of species in the count and the diversity (indices of Simpson and Shannon) decreased significantly in S+C, and that goes also for the dissimilarity index of Dyer. No changes were found in N.The first component (PC 1) of the principal component analysis explains 61% of total variance. PC 1 is correlated with log [SO₄] (r=0.83, p<0.001) and even better (r=0.95, p<0.001) with the relative sulphate concentration,i.e. the ratio of sulphate to all major anions (sulphate, chloride, bicarbonate). All old samples have low scores on PC 1, recent samples have low scores on the second (PC 2) and third (PC 3) principal component. Old samples have high scores on PC 2 and PC 3, explaining 9 and 6% of total variance, respectively.The orginal variation, caused by regional factors, is replaced by a SO₄ ^2– controlled variation. PC 1 is nearly completely determined by the relative abundance ofEunotia exigua. This species, which is known to be very resistant to pollution by sulphur, aluminium and heavy metals, increased largely from 1920 to 1978.In spite of the rather homogeneous distribution of wet sulphate deposition in the Netherlands, substantial differences in SO₄ ^2– content in the pools are observed, being lowest in N (0.13–0.48 meq.l^–1) and highest in S+C (0.38–1.65 meq.l^–1). Sulphate is positively correlated with calcium, aluminum and magnesium but negatively with factors that characterize humic acid waters (e.g. permanganate-consumption, iron and the ratio of univalent to divalent cations). Sulphate concentration depends on the intensity of sulphate reduction, accumulation by dry deposition in surrounding forests of Scots pine, drought and atmospheric deposition.     

Effects of Magnesium on Intact Chloroplasts: I. EVIDENCE FOR ACTIVATION OF (SODIUM) POTASSIUM/PROTON EXCHANGE ACROSS THE CHLOROPLAST ENVELOPE

Exogenous Mg²⁺ (2 millimolar) altered the stromal pH of intact spinach chloroplasts. Without added KCl in the medium, Mg²⁺ decreased the stromal pH in the light by approximately 0.3 pH unit. External KCl (25 millimolar) largely prevented the acidification caused by Mg²⁺. Effects on the stromal pH were not caused by changes in H⁺ pumping across the thylakoid membrane because Mg²⁺ had no effect on the light-induced quenching of atebrin fluorescence by intact chloroplasts. However, Mg²⁺ affected H⁺ fluxes across the envelope. Addition of Mg²⁺ to intact chloroplasts in the dark caused a significant acidification of the medium that was dependent on the presence of K⁺.     

Effects of Magnesium on Intact Chloroplasts : II. CATION SPECIFICITY AND INVOLVEMENT OF THE ENVELOPE ATPase IN (SODIUM) POTASSIUM/PROTON EXCHANGE ACROSS THE ENVELOPE

Addition of exogenous Mg²⁺ (2 millimolar) to illuminated intact spinach (Spinacia oleracea L.) chloroplasts caused acidification of the stroma and a 20% decrease in stromal K⁺. Addition of K⁺ (10-50 millimolar) reversed both stromal acidification and K⁺ efflux from the chloroplast caused by Mg²⁺. These data suggested that Mg²⁺ induced reversible H⁺/K⁺ fluxes across the chloroplast envelope. Ca²⁺ and Mn²⁺ (2 millimolar) were as effective as 4 millimolar Mg²⁺ in causing K⁺ efflux from chloroplasts and inhibition of O₂ evolution. In contrast, 10 millimolar Ba²⁺ induced only a small amount of inhibition. The lack of strong inhibition by Ba²⁺ indicated that the effects of divalent cations such as Mg²⁺ cannot be attributed to generalized electrostatic interactions of the cation with the chloroplast envelope. With the chloroplasts used in this study, stromal acidification caused by 2 millimolar Mg²⁺ was small (0.07 to 0.15 pH units), but sufficient to account for the inhibition of O₂ evolution (43%) induced by Mg²⁺.     

Ecology and management of moorland pools: balancing acidification and eutrophication

Moorland pools originally are shallow, often hydrologically isolated, soft-water bodies, with a low productivity. Some thousands of moorland pools originated from the late Pleistocene onwards in the heathland landscape in The Netherlands and adjacent areas, where soils have a poor buffering capacity. As the pools are largely fed by atmospheric precipitation, they are very vulnerable to changes in the environment, e.g. eutrophication and acidification. Moorland pools are exposed to very high rates of wet atmospheric deposition: 44–50 mmol m⁻² yr⁻¹ sulphate and 84–103 mmol m ⁻² yr⁻¹ ammonium. Mass budgets indicate that 20–70% of the input of sulphate by precipitation is reduced, 40–100% of the ammonium input escapes to the air or sediments, apparently due to nitrification, and 90–100% of incoming nitrate disappears. The production of alkalinity ranges from 12 to 52 meq m⁻² yr⁻¹. The efficiency of these processes augments with pH-values of surface water increasing from 4.1 to 5.4. The accumulation of reduced sulphur compounds in the sediments is a threat in extremely dry summers, when desiccation causes oxydation of these compounds, resulting in very low pH-values (≤ 3.7). Acidification by acid atmospheric deposition and eutrophication by agricultural acidification are the main threats to the moorland pool ecosystems and affect the species composition of assemblages of aquatic macrophytes, desmids, diatoms, macrofauna, fishes and amphibians, as has been shown by comparison of old and recent records on their distribution and paleolimnological methods. Afforestation exacerbates acidification and also reduces wind dynamics. Particularly the decrease of isoetids and desmids by both processes indicate the biological impoverishment of the pools. Reductions of (potential) acid atmospheric deposition to less than 40 mmol m⁻² yr and of ammonia to less than 30 mmol m⁻² yr are necessary for recovery of the moorland pools. Methods for the addition of buffering material to a number of moorland pools, to counteract acidification until these deposition rates have lowered sufficiently, are given, as well as other methods for restoring the biological quality of moorland pools.     

Long-term and seasonal changes in the chemical composition of precipitation and surface waters of lakes and tarns in the English Lake District

SUMMARY. The composition of bulk (wet and dry) precipitation in 1975 and 1976 was similar to that found 22 years previously. In 1975, mean values for nine precipitation samplers at one site (Wraymires) ranged from pH 4.3 to 4.5; similar values were obtained in 1976. Samplers covered with fine-mesh plastic gauze caught substantially more Ca²⁺ and K⁺ than open samplers, but pH and SO^2-₄+ NO₃^- concentrations were similar in open and covered samplers. In precipitation, c. 50% of H⁺ was balanced by NO₃^- and c. 50% by SOi; 80% of the SO^2-₄ was balanced by Ca²⁺ and Mg²⁺. Conccntrations of major cations (H⁺, Na⁺, K⁺,Ca²⁺, Mg²⁺) and anions (CI^-, NO₃^- SO^2-₄ and alkalinity [Alk—largely HCO₃^-]) in upland water- bodies were similar to those found in precipitation, but pH levels were generally higher and above 6.0 m some tarns. At lower altitudes, on base-rich roeks and soils, Ca²⁺ and Alk become dominant. Results of a survey of lakes and tarns in 1974–78 are compared with a survey in 1953–56 and published data (chiefly for pH and Alk) for 1947–50, 1932 and 1928. Comparisons are also made with other measurements of Alk in three productive lakes (Blelham Tarn, Esthwaite Water and Windermere) for 1936–39 and 1945–80. Winter levels of NO₃-N, PO₄-P and Si are given for these lakes; although the first two have increased during the late 1960s and the 1970s there has been no significant change in the last. NO₃^- and probably some SO^2-₄. In productive lakes a substantial (c. 50%) rise in mean Alk occurred during the late 1960s and the 1970s, possibly related to increased winter levels of NO₃-N and PO₄-P derived from sewage and fertilizers. In this period the maximum pH levels reached in summer were notably high, sometimes exceeding pH 10. The rise in Alk, conductivity and pH of surface waters is influenced by climatic factors (a decade of drier years), sewage input and biological productivity within the lakes. Considerable seasonal fluctuations in the concentrations of major ions, a characteristic feature of surface waters in the English Lake District, are illustrated and some implications for cation-anion balance briefly discussed. Mid-winter concentrations are usually high forNa⁺, K⁺, Cl^-. NO₃^-and low for Ca²⁺, Mg²⁺, Alk. SO^2-₄. Alkalinity. pH and conductivity of Lake District tarns and lakes show no signs of acidification during the period 1928–80. On the contrary, productive lakes have become more alkaline and some unproductive low-alkalinity (< 100 μ-equiv. 1^-1) lakes also show signs of alkalization, with increased mean concentrations of Na⁺. Ca²⁺ and Mg²⁺, balanced by Alk.     

Surface Charge-Mediated Effects of Mg on K Flux across the Chloroplast Envelope Are Associated with Regulation of Stromal pH and Photosynthesis

Studies of Spinacia oleracea L. were undertaken to characterize further how Mg²⁺ external to the isolated intact chloroplast interacts with stromal K⁺, pH, and photosynthetic capacity. Data presented in this report were consistent with the previously developed hypothesis that millimolar levels of external, unchelated Mg²⁺ result in lower stromal K⁺, which somehow is linked to stromal acidification. Stromal acidification directly results in photosynthetic inhibition. These effects were attributed to Mg²⁺ interaction (binding) to negative surface charges on the chloroplast envelope. Chloroplast envelope-bound Mg²⁺ was found to decrease the envelope membrane potential (inside negative) of the illuminated chloroplast by 10 millivolts. It was concluded that Mg²⁺ effects on photosynthesis were likely not mediated by this effect on membrane potential. Further experiments indicated that envelope-bound Mg²⁺ caused lower stromal K⁺ by restricting the rate of K⁺ influx; Mg²⁺ did not affect K⁺ efflux from the stroma. Mg²⁺ restriction of K⁺ influx appeared consistent with the typical effects imposed on monovalent cation channels by polyvalent cations that bind to negatively charged sites on a membrane surface near the outer pore of the channel. It was hypothesized that this interaction of Mg²⁺ with the chloroplast envelope likely mediated external Mg²⁺ effects on chloroplast metabolism.     

Evidence for an Amiloride-Inhibited Mg/2H Antiporter in Lutoid (Vacuolar) Vesicles from Latex of Hevea brasiliensis

Lutoids represent a lysosomal microvacuolar compartment of rubber-tree (Hevea brasiliensis) latex. We observed acidification of isolated vesicles after imposing an outward Mg²⁺ diffusion gradient and dissipation of a preformed pH gradient in the presence of exogenous Mg²⁺. These results suggest the presence of a Mg²⁺/H⁺ antiporter. The maximum Mg²⁺/H⁺ exchange rate was observed at pH 8.5. The K_m values for Mg²⁺ (2.6 mm) were identical for both influx and efflux experiments. When membrane potential was clamped at zero with K⁺ and valinomycin, the response of the membrane potential probe oxonol VI showed that the Mg²⁺/H⁺ exchange was electroneutral. Mg²⁺/H⁺ exchange was inhibited by amiloride and imipramine. Both the inhibiting concentration range and the K_m for Mg²⁺ are similar to those reported for the Mg²⁺/2Na⁺ antiporter in animals cell. These data are consistent with the existence of a Mg²⁺/2H⁺ antiporter in a plant tonoplast.     

Diversity of Carbon Monoxide-Oxidizing Bacteria in Five Lakes on the Qinghai-Tibet Plateau,China

Carbon monoxide-oxidizing (COX) bacteria play an important role in controlling the flux of carbon monoxide among natural reservoirs, and thus studying their diversity in natural environments is of great significance to understanding the carbon cycle. In this study, the COX bacterial diversity was investigated in five lakes (Erhai Lake, Gahai Lake1, Gahai Lake2, Xiaochaidan Lake, Lake Chaka) on the Qinghai-Tibet Plateau and its correlation with environmental variables of the lakes was explored. Phylogenetic analyses showed that the CO-oxidizers were dominated by Proteobacteria and Actinobacteria in the Qinghai-Tibet Plateau lakes, and their relative abundance varied with salinity: in the freshwater Erhai Lake, the COX bacteria in the water were dominated by the Betaproteobacteria, in contrast to the Actinobacteridae dominance in the sediment; in the saline and hypersaline lakes of Gahai Lake1, Gahai Lake2 and Xiaochaidan Lake, alphaproteobacterial COX bacteria were dominant in the water, whereas Actinobacteridae and alphaproteobacterial COX bacteria were dominant in the sediment. In the hypersaline Lake Chaka, an unknown COX bacterial clade and alphaproteobacterial COX bacteria were dominant in the water and sediment, respectively. Statistical analyses showed that salinity, pH, and major ions (e.g., K⁺, Na⁺, Ca²⁺, Mg²⁺, SO₄ ^2-, and Cl^-) were important factors affecting the COX bacterial community compositions in the investigated lakes. Overall, our results provided insights into the COX bacterial diversity in Qinghai-Tibetan lakes.     

Studies of (Na+ + K+)-sensitive ATPase activity in pig lymphocytes. Effects of concanavalin A

(Na⁺ + K⁺)-ATPase activity is demonstrated in plasma membranes from pig mesenteric lymph nodes. After dodecyl sulfate treatment plasma membranes have an 18-fold higher (Na⁺ + K⁺)-ATPase activity, while their ouabain-insensitive Mg²⁺-ATPase is markedly lowered. A solubilized (Na⁺ + K⁺)-ATPase fraction, obtained by Lubrol WX treatment of the membranes, has very high specific activity (21μmol P_i/h per mg protein). Concanavalin A has no effect on these partially purified (Na⁺ + K⁺)-ATPase, while it inhibits (40%) this activity in less purified fractions which still contain Mg²⁺-ATPase activity.     

Studies on the System Regulating Proton Movement across the Chloroplast Envelope : Effects of ATPase Inhibitors, Mg, and an Amine Anesthetic on Stromal pH and Photosynthesis

Studies were undertaken to further characterize the spinach (Spinacea oleracea) chloroplast envelope system, which facilitates H⁺ movement into and out of the stroma, and, hence, modulates photosynthetic activity by regulating stromal pH. It was demonstrated that high envelope-bound Mg²⁺ causes stromal acidification and photosynthetic inhibition. High envelope-bound Mg²⁺ was also found to necessitate the activity of a digitoxinand oligomycin-sensitive ATPase for the maintenance of high stromal pH and photosynthesis in the illuminated chloroplast. In chloroplasts that had high envelope Mg²⁺ and inhibited envelope ATPase activity, 2-(diethylamino)-N-(2,6-dimethylphenyl)acetamide was found to raise stromal pH and stimulate photosynthesis. 2-(Diethylamino)-N-(2,6-dimethylphenyl)acetamide is an amine anesthetic that is known to act as a monovalent cation channel blocker in mammalian systems. We postulate that the system regulating cation and H⁺ fluxes across the plastid envelope includes a monovalent cation channel in the envelope, some degree of (envelope-bound Mg²⁺ modulated) H⁺ flux linked to monovalent cation antiport, and ATPase-dependent H⁺ efflux.     

Relationships between chloride and major cations in precipitation and streamwaters in the Windermere catchment (English Lake District)

SUMMARY. 1. The ranges of concentrations for pH, CV. Na⁺. K⁺Ca²⁺, Mg²⁺ are given for streams draining igneous rocks (Borrowdale Volcanics) and sedimentary muds, silts and shales (Silurian Slates) in the catchment of Windermere (230 km²). Impacts on the biota are briefly discussed. Relative contributions of inputs from various sources are examined: precipitation, rocks and soils, sewage, deicing salt used on highways./ 2. In bulk precipitation, ratios of Na⁺/CV (as μequiv. I^?1) ranged from 0.41 to 1.83 over a 2-year period. The overall volume-weighted mean ratio was 0.86, as in seawater, hut 2′4%(1975) and 5.7% (1976) of Cl^? was non-marine in origin, being balanced by H ⁺ (in winter), K and Ca²⁺ (in summer). In moorland headwater streams, CI^? is largely derived from precipitation: there is a pronounced annual cycle of midwinter high and midsummer low concentrations unrelated to stream discharge. Na* and K⁺ display similar cycles but Na⁺, Ca2⁺ and Mg²⁺ (and pH) are discharge-related due to leaching from rocks and soils: 10–20% Na+, 15–17% Mg²⁺ and 65–75% Ca²⁺ are so-derived whereas K+ comes from precipitation. Na⁺/Cl⁺ ratios in streams on Borrowdale Volcanics alter seasonally, with midsummer values >1. Lower values occur in streams on Silurian Slates where some CI^? is apparently derived from rocks. 3. Seasonal changes in streamwater concentrations of Cl, Na⁴ andK⁺are exponentially related to time. Instantaneous rates of change i day-1¹) are compared in relation to position in the catchment and inputs from anthropogenic sources. Deicing salt has raised (10–100-fold) the concentrations of Na^* and Cl^? in streams on mountain passes; the effects persist throughout the year.     

Effectiveness of potassium sulfate in mitigating salt-induced adverse effects on different physio-biochemical attributes in sunflower (Helianthus annuus L.)

To assess whether foliar application of K+S as potassium sulfate (K₂SO₄) could alleviate the adverse effects of salt on sunflower (Helianthus annuus L. cv. SF-187) plants, a greenhouse experiment was conducted. There were two NaCl levels (0 and 150 mM) applied to the growth medium and six levels of K+S as K₂SO₄ (NS (no spray), WS (spray of water+0.1% Tween 20 solution), 0.5% K+0.21% S, 1.0% K+0.41% S, 1.5% K+0.62% S, and 2.0% K+0.82% S in 0.1% Tween-20 solution) applied two times foliarly to non-stressed and salt-stressed sunflower plants. Salt stress markedly repressed the growth, yield, photosynthetic pigments, water relations and photosynthetic attributes, quantum yield (F_v/F_m), leaf and root K⁺, Mg²⁺, P, Ca²⁺, N as well as K⁺/Na⁺ ratios, while it enhanced the cell membrane permeability, and leaf and root Na⁺ and Cl⁻ concentrations. Foliar application of potassium sulfate significantly improved growth, achene yield, photosynthetic and transpiration rates, stomatal conductance, water use efficiency, leaf turgor and enhanced shoot and leaf K⁺ of the salt-stressed sunflower plants, but it did not improve leaf and root Na⁺, Cl⁻, Mg²⁺, P, Ca²⁺, N as well as K⁺/Na⁺ ratios. The most effective dose of K+S for improving growth and achene yield was found to be 1.5% K+0.62% S and 1% K+0.41% S, respectively. Improvement in growth of sunflower plants due to exogenously applied K₂SO₄ was found to be linked to enhanced photosynthetic capacity, water use efficiency, leaf turgor and relative water content.     

Effects of CO2 and nitrogen fertilization on vegetation and soil nutrient content in juvenile ponderosa pine

This paper summarizes the data on nutrient uptake and soil responses in opentop chambers planted with ponderosa pine (Pinus ponderosa Laws.) treated with both N and CO₂. Based upon the literature, we hypothesized that 1) elevated CO₂ would cause increased growth and yield of biomass per unit uptake of N even if N is limiting, and 2) elevated CO₂ would cause increased biomass yield per unit uptake of other nutrients only by growth dilution and only if they are non-limiting. Hypothesis 1 was supported only in part: there were greater yields of biomass per unit N uptake in the first two years of growth but not in the third year. Hypothesis 2 was supported in many cases: elevated CO₂ caused growth dilution (decreased concentrations but not decreased uptake) of P, S, and Mg. Effects of elevated CO₂ on K, Ca, and B concentrations were smaller and mostly non-significant. There was no evidence that N responded in a unique manner to elevated CO₂, despite its unique role in rubisco. Simple growth dilution seemed to explain nutrient responses in almost all cases.There were significant declines in soil exchangeable K⁺, Ca²⁺, Mg²⁺ and extractable P over time which were attributed to disturbance effects associated with plowing. The only statistically significant treatment effects on soils were negative effects of elevated CO₂ on mineralizeable N and extractable P, and positive effects of both N fertilization and CO₂ on exchangeable Al³⁺. Soil exchangeable K⁺, Ca²⁺, and Mg²⁺ pools remained much higher than vegetation pools, but extractable P pools were lower than vegetation pools in the third year of growth. There were also large losses of both native soil N and fertilizer N over time. These soil N losses could account for the observed losses in exchangeable K⁺, Ca²⁺, Mg²⁺ if N was nitrified and leached as NO ₃ ^– .     

Cadmium accumulation and its effects on intracellular ion pools in a brewing strain of Saccharomyces cerevisiae

The presence of glucose resulted in a two- to three-fold increase in levels of Cd²⁺accumulated by Saccharomyces cerevisiae after 5 h compared with those observed in the absence of glucose. However, time-dependent Cd²⁺ uptake continued in the absence of glucose over 5 h, resulting in an appreciable increase in cellular Cd²⁺levels. Substantial K⁺ efflux but little Mg²⁺ and negligible Ca²⁺release was observed. Cell fractionation revealed that the bulk of intracellular Cd²⁺ was located in the vacuolar (25%) and bound (60%) fractions. Accumulation of Cd²⁺ ions impacted most noticeably on K⁺ rather than Mg²⁺ levels in intracellular compartments. Cytoplasmic and particularly vacuolar K⁺ levels decreased as Cd²⁺ sequestration continued resulting in increased extracellular levels. In contrast, corresponding intracellular Mg²⁺ pools were only modestly affected with a slight increase and decrease observed in the cytoplasmic and vacuolar fractions respectively. However, levels of bound Mg²⁺ decreased in response to continued Cd²⁺ accumulation. Received 07 March 1999/ Accepted in revised form 26 June 1999     

Alkaline pH,membrane potential,and magnesium cations are negative modulators of purine nucleotide inhibition of H+ and Cl− transport through the uncoupling protein of brown adipose tissue mitochondria

Modulators of purine nucleotide (PN) inhibition of H⁺ and Cl^– transport mediated by the uncoupling protein (UP) of brown adipose tissue (BAT) mitochondria were studied: Alkalinization strongly diminishes GDP inhibition of H⁺ transport ( log IC₅₀=–pH_out), while more intensive inhibition of Cl^– transport is only slightly altered. Higher decreases GDP inhibition of H⁺ transport. Mg²⁺, but not palmitoyl-CoA, decreases PN inhibitory ability.Simulations of conditions similar to those found in BAT cells in the resting state and in the thermogenic state showed that three factors act in concert: pH, Mg²⁺, and free fatty acids (FFA): (a) with endogenous FFA present and 2 mM ATP and 0.5 mM AMP (pH 7.1), H⁺ transport was inhibited by 95% in the absence of Mg²⁺, while by 60% with Mg²⁺; (b) 0.5 mM ATP and 1 mM AMP, H⁺ transport was inhibited by 40% without Mg²⁺ and by 30% with Mg²⁺. State b thus represents a model thermogenic state, while state a represents a resting state. However, the latter statein vivo must be accomplished either by combustion or FFA or by elimination of Mg²⁺ to attain a total inhibition of H⁺ transport (cf. a).The model of UP possessing two independent channels, an H⁺ channel and a Cl^– channel, controlled from a single PN-binding site is supported by independent kinetics by different pH dependence of H⁺ and Cl^– transport, and by a lower sensitivity of H⁺ transport to PN inhibition.     

Integration of lakes and streams in a landscape perspective: the importance of material processing on spatial patterns and temporal coherence

1. We studied the spatial and temporal patterns of change in a suite of twenty‐one chemical and biological variables in a lake district in arctic Alaska, U.S.A. The study included fourteen stream sites and ten lake sites, nine of which were in a direct series of surface drainage. All twenty‐four sites were sampled between one and five times a year from 1991 to 1997. 2. Stream sites tended to have higher values of major anions and cations than the lake sites, while the lake sites had higher values of particulate carbon, nitrogen, phosphorous and chlorophyll a. There were consistent and statistically significant differences in concentrations of variables measured at the inlet versus the outlet of lakes, and in variables measured at upstream versus downstream sites in the stream reaches which connect the lakes. In‐lake processing tended to consume alkalinity, conductivity, H⁺, DIC, Ca²⁺, Mg²⁺, CO₂, CH₄, and NO₃^–, and produce K⁺ and dissolved organic carbon (DOC). In‐stream processing resulted in the opposite trends (e.g. consumption of K⁺ and DOC), and the magnitudes of change were often similar to those measured in the lakes but with the opposite sign. 3. Observed spatial patterns in the study lakes included mean concentrations of variables which increased, decreased or were constant along the lake chain from high to low altitude in the catchment (stream sites showed no spatial patterns with any variables). The strongest spatial patterns were of increasing conductivity, Ca²⁺, Mg²⁺, alkalinity, dissolved inorganic carbon and pH with lake chain number (high to low altitude in the basin). These patterns were partly determined by the effect of increasing catchment area feeding into lakes further downslope, and partly by the systematic processing of materials in lakes and in the stream segments between lakes. 4. Synchrony (the temporal coherence or correlation of response) of variables across all lakes ranged from 0.18 for particulate phosphorus to 0.90 for Mg²⁺ the average synchrony for all twenty‐one variables was 0.50. The synchronous behaviour of lake pairs was primarily related to the spatial location or proximity of the lakes for all variables taken together and for many individual variables, and secondarily, to the catchment to lake area ratio and the water residence time. 5. These results illustrate that, over small geographic areas, and somewhat independent of lake or stream morphometry, the consistent and directional (downslope) processing of materials helps produce spatial patterns which are coherent over time for many limnological variables. We combine concepts from stream, lake and landscape ecology, and develop a conceptual view of landscape mass balance. This view highlights that the integration of material processing in both lakes and rivers is critical for understanding the structure and function of surface waters, especially from a landscape perspective.     

Participation of vacuoles in regulation of levels of K+, Mg2+ and orthophosphate ions in cytoplasm of the yeast Saccharomyces carlsbergensis

Intracellular distributions of K⁺, Mg²⁺ and orthophosphate under various conditions of cultivation or incubation of the yeast Saccharomyces carlsbergensis were studied by differential extraction of ion pools. The decisive role of vacuolar compartmentation of ions in regulation of K⁺, Mg²⁺ and orthophosphate levels in the yeast cytoplasm was shown. The content of intracellular K⁺ and Mg²⁺ in yeast increased or decreased primarily depending on the increase or decrease in the vacuolar ion pool. The levels of K⁺ and Mg²⁺ in the cytoplasm were practically unchanged. Vacuoles were involved in regulation of Mn²⁺ concentration in the cytoplasm of the yeast S. carlsbergensis accumulating this ion in the presence of glucose. Alongside the vacuolar compartmentation, the chemical compartmentation, i. e. formation of bound Mg²⁺, Mn²⁺ and K⁺ was, evidently, also involved in the control of ion levels in the cytoplasm. The orthophosphate level in the yeast cytoplasm was regulated by its accumulation in vacuoles and biosynthesis of inorganic polyphosphates in these organelles. The biosynthesis of low-molecular weight polyphosphates occurred parallel to the accumulation of Mg²⁺ or Mn²⁺ in vacuoles, thus confirming the availability of the other mechanism for the transport of these ions through the tonoplast differing from the transport mechanism through the plasmalemma.     

Comparison of the effects of one-side- and two-side Mg2+ on the reconstitution of mitochondrial H+-ATPase

Three types of proteoliposome containing mitochondrial H⁺-ATPase have been prepared: Mg²⁺-‘free’, one-side and two-side Mg²⁺-containing proteoliposomes. The ATPase activity as well as its sensitivity to oligomycin or N,N'-dicyclohexylcarbodiimide of the three proteoliposome preparations has been compared. They decreased in the order : L ·(H⁺-ATPase)_+Mg²⁺ > L · (H⁺-ATPase)_+Mg²⁺ > L · (H⁺-ATPase)_−Mg²⁺. The fluidity of the proteoliposomes has also been compared by fluorescence polarization probes diphenylhexatriene (DPH) or 7-(9-anthroyloxy)stearic acid (7-AS). The degree of polarization for DPH in these proteoliposomes decreased in the order: L · (H⁺-ATPase)_+Mg²⁺ > L · (H⁺-ATPase)_+Mg²⁺ > L · (H⁺-ATPase)_−Mg²⁺, while that for 7-AS: L · (H⁺-ATPase)_+Mg²⁺ ≈ L · (H⁺-ATPase)_+Mg²⁺ > L · (H⁺-ATPase)_−Mg²⁺.Lipid fluidityMitochondrial H⁺-ATPaseOne-side Mg²⁺ effectTwo-side Mg²⁺ effectLipid-protein interaction     

Cations stimulate proton pumping in Catharanthus roseus cells: implication of a redox system?

Abstract During growth, cultured Catharanthus oseus cells produce a transient acidification of the culture medium that may be controlled by cations. The removal of divalent ions from the medium by the chelator EGTA resulted in an inhibition of this acidification. Conversely, acidification can be stimulated by the addition of Ca²⁺, Mg²⁺ and La³⁺ in the basal medium. This acidification process and the proton-linked redox pump previously described (Marigo & Belkoura, 1985) respond in a similar manner to cations. These two systems, which are both inhibited by the Ca²⁺ -calmodulin antagonist calmidazolium, could be regulated by the Ca²⁺-calmodulin complex. By using ionic surfactant (CP⁺, SDS^?) it was demonstrated that the net surface charge of the plasmalemma plays a role in the activation of the two pumping processes. These results are interpreted to indicate that a transmembrane redox system could provide the energy for electrogenic proton extrusion.     

Ca-Mg-ATPase activity in brain coated microvesicles purified on immunosorbents

Coated microvesicle fractions isolated from ox forebrain cortex by the ultracentrifugation procedure of Pearse (1) and by the modified, less time consuming method of Keen et al (2) had comparable Ca²⁺+Mg²⁺ dependent ATPase activities (about 9 μmol/h per mg protein). The Na⁺+K⁺+Mg²⁺ dependent ATPase activity was 3.2 μmol/h per mg (±1.0, S.D., n=3) when microvesicles were prepared according to (1) and 1.5 μmol/h per mg (±1.0, S.D., n=3) when prepared according to (2).Oligomycin, ruthenium red, and trifluoperazine, inhibitors of Ca²⁺ transport in mitochondria and erythrocyte membranes had no effect on Ca²⁺+Mg²⁺ dependent ATPase from any of the preparations.As demonstrated both by ATPase assays and electron microscopy, coated microvesicles could be bound to immunosorbents prepared with poly-specific antibodies against a coated microvesicle fraction obtained by the method of Pearse (1). The binding could be inhibited by dissolved coat protein using partially purified clathrin. The fraction of coated vesicles eluted from the immunosorbent was purified relative to the starting material as judged by electron microscopy.The Ca²⁺+Mg²⁺ ATPase activity and calmodulin content was copurified with the coated microvesicles and the specific activity of Na⁺+K⁺+Mg²⁺ ATPase was decreased.Na⁺+K⁺+Mg²⁺ dependent ATPase activity in the coated microvesicle fraction could be ascribed to membranes with the appearance of microsomes. These membranes were also bound to the immunosorbents, but the binding was not influenced by clathrin. The capacity of the immunosorbents for these membranes was less than for the coated microvesicles, resulting in a decrease of Na⁺+K⁺+Mg²⁺ dependent ATPase activity in the eluted coated microvescile fraction.It was concluded that Ca²⁺+Mg²⁺ ATPase activity is not a contamination from plasma membrane vesicles or mitochondrial membranes but seems to be an integral part of the coated vesicle membrane.