Further Studies on the Roles of Sodium and Potassium in the Generation of the Electro-Olfactogram : Effects of mono-, di-, and trivalent cations

In the negative EOG-generating process a cation which can substitute for Na⁺ was sought among the monovalent ions, Li⁺, Rb⁺, Cs⁺, NH₄⁺, and TEA⁺, the divalent ions, Mg⁺⁺, Ca⁺⁺, Sr⁺⁺, Ba⁺⁺, Zn⁺⁺, Cd⁺⁺, Mn⁺⁺, Co⁺⁺, and Ni⁺⁺, and the trivalent ions, Al⁺⁺⁺ and Fe⁺⁺⁺. In Ringer solutions in which Na⁺ was replaced by one of these cations the negative EOG's decreased in amplitude and could not maintain the original amplitudes. In K⁺-Ringer solution in which Na⁺ was replaced by K⁺, the negative EOG's reversed their polarity. Recovery of these reversed potentials was examined in modified Ringer solutions in which Na⁺ was replaced by one of the above cations. Complete recovery was found only in the normal Ringer solution. Thus, it was clarified that Na⁺ plays an irreplaceable role in the generation of the negative EOG's. The sieve hypothesis which was valid for the positive EOG-generating membrane or IPSP was not found applicable in any form to the negative EOG-generating membrane. The reversal of the negative EOG's found in K⁺- , Rb⁺- , and Ba⁺⁺-Ringer solutions was attributed to the exit of the internal K⁺. It is, however, not known whether or not Cl^- permeability increases in these Na⁺-free solutions and contributes to the generation of the reversed EOG's.     

Production of Alkaline Lipase by Corynebacterium paurometabolum, MTCC 6841 Isolated from Lake Naukuchiatal, Uttaranchal State, India

A moderately psychrophilic bacterium Corynebacterium paurometabolum MTCC 6841 (gram positive, short rod type) producing extracellular alkaline lipase was isolated from Lake Naukuchiatal, Uttaranchal, India. The bacterium was able to grow within a broad range of pH (5–10). Soyabean oil and olive oil served as the best carbon sources for lipase production. The bacterium preferred inorganic nitrogenous compounds, NaNO₃ and KNO₃, over organic nitrogenous compound for its growth. Maximum lipase production occurred at 25°C and 8.5 pH. The enzyme activity was found to be maximum at the same values of temperature and pH. The enzyme was reasonably stable in the presence of various organic solvents. No significant effect of Ca⁺, Cu⁺⁺, Fe⁺⁺, Na⁺, K⁺, Mg⁺⁺, Mn⁺, NH4⁺, Co⁺⁺ ions over enzyme activity was detected. Treatment with EDTA reduced the activity to nearly one half.     

23Na NMR investigation of the interaction between DNA and divalent metallic cations

The aim of this study is to follow the thermodynamic behaviour of Na⁺ ions, acting as natural counterions of DNA, in the presence of divalent metal ions, by using the²³Na NMR technique. With the help of the²³Na entropy of fluctuations concept introduced by Lenk, we propose the following decreasing sequence: Mg⁺⁺, Zn⁺⁺, Cd⁺⁺, Mn⁺⁺, and Cu⁺⁺, for the magnitude of divalent metal ions interactions with DNA phosphate sites.     

3H-mepyramine binding to histamine H1-receptors in guinea pig lung: Characteristics and regulation by ions

The antogonist [³H]-mepyramine is used to label histamine H₁-receptors in guinea pig lung. Scatchard analysis reveals two classes of binding sites. Monovalent cations decrease steady-state binding (Na⁺ > Li⁺ > K⁺), while divalent cations (Mg⁺⁺, Ca⁺⁺, Mn⁺⁺, Ba⁺⁺) exhibit a biphasic curve, increasing binding at low concentrations and decreasing it at higher levels. Na⁺ decreases both affinity and number of binding sites. Dissociation curve shows two components, and Na⁺ accelerates the rate of dissociation of the slower component. GTP does not affect the binding of the antagonist ³H-Mepyramine.     

Effect of different water salinity levels and organic matter application on the composition of water soluble and exchangeable bases in a brackishwater fish pond soil

Behaviour of different water soluble and exchangeable bases in a brackishwater fish pond soil was studied under four levels of water salinity, in combination with and without organic matter application. The results showed average content of water soluble bases to increase with increase in water salinity. The bases were dominated by Na⁺ followed by Mg⁺⁺, Ca⁺⁺ and K⁺ in decreasing order. SAR values of water increased with increase in water salinity and decreased slightly on organic matter treatment.Total content of exchangeable bases in soils was fairly high and was dominated by Ca⁺⁺ and Mg⁺⁺, followed by Na⁺ and K⁺ respectively. Amount of exchangeable Ca⁺⁺ + Mg⁺⁺ decreased while that of Na⁺ increased with increase in water salinity levels. Amount of exchangeable K⁺ did not show any appreciable change. Application of organic matter tended to increase the exchangeable Ca⁺⁺ + Mg⁺⁺ content and decrease the amount of exchangeable Na⁺ in the soil, while exchangeable K⁺ content remained practically unaffected due to organic matter treatment.Formed part of a Ph.D. thesis submitted to Bidhan Chandra Agricultural University, India in 1978Formed part of a Ph.D. thesis submitted to Bidhan Chandra Agricultural University, India in 1978     

Muscle: A Three Phase System : The partition of divalent ions across the membrane

The partition of sulfate, Ca⁺⁺, and Mg⁺⁺ across the membrane of the sartorius muscle has been studied, and the effect of various concentrations of these ions in the Ringer solution on the cellular level of Na⁺, K⁺, and Cl^- has been determined. The level of the three divalent ions in toad plasma and muscle in vivo has been assayed. Muscle was found to contain an almost undetectable amount of inorganic sulfate. Increases in the external level of these ions brought about increases in intracellular content, calculated from the found extracellular space as determined with radioiodinated serum albumin or inulin. Less of the cell water is available to sulfate than to Cl^-, and the Mg⁺⁺ space is less than the Na⁺ space. An amount of muscle water similar to that found for Li⁺ and I^- appears to be available to these divalent ions. Sulfate efflux from the cell was extremely rapid, and it was not found possible to differentiate kinetically between intra- and extracellular material. These results are consistent with the theory of a three phase system, assuming the muscle to consist of an extracellular phase and two intracellular phases. Mg⁺⁺ and Ca⁺⁺ are adsorbed onto the ordered phase, and increments in cellular content found on raising the external level are assumed to occur in the free intracellular phase.     

Combined effects of waterlogging and salinity on electrochemistry, water-soluble cations and water dispersible clay in soils with various salinity levels

The combination effects of waterlogging and salinity on redox potential (Eh), pH, electric conductivity (EC), water-soluble cations (NH₄ ⁺, K⁺, Na⁺, Ca²⁺, Mg²⁺, Fe²⁺, and Mn²⁺) and water-dispersible clay (WDC) were studied in six soils collected near salt lakes in western Australia. The soils with various salinity levels were incubated under a waterlogged condition at 30 °C for 12 weeks. The Eh, pH, EC, and cations of soil solutions were monitored over the waterlogged period. The Eh values generally dropped to the lowest point within 12 days of waterlogging, then increased slightly, and reached equilibrium after 4 weeks of waterlogging. Increasing salinity levels increased soil Eh. While waterlogging increased soil pH in the first 3–4 weeks, increasing salinity level decreased soil pH during the entire waterlogging period. Waterlogging increased the EC values in the first 2 weeks, partly due to dissolution of insoluble salts. The concentrations of water-soluble NH₄ ⁺ were significantly increased with salinity level and waterlogging, and reached maximum values at week 2, and then declined to the initial level. Waterlogging and salinity increased the concentrations of water-soluble K⁺, Ca²⁺, Mg²⁺, Fe²⁺, and Mn²⁺ ions, but the magnitudes of changes were greatly affected by soil properties. Increases in water-soluble K⁺, Ca²⁺ and Mg²⁺ were attributed to increased solubility of insoluble salts, and increased competition for the adsorption sites of the soil exchange complex due to elevated concentrations of Na⁺, Fe²⁺ and Mn²⁺. Increases in water-soluble Fe²⁺ and Mn²⁺ induced by waterlogging were attributed to the dissolution of Fe and Mn oxides under reduced conditions. Waterlogging increased, but salinity decreased, the amounts of water-dispersible clay in the soils of low EC value. The higher salinity level can counteract the adverse effect of waterlogging on clay flocculation.     

Ionic Resistance in Strains of the Tetrahymena pyriformis Complex1

ABSTRACT. Strains of Tetrahymena thermophila were examined in an attempt to establish what role certain ions (Na⁺, K⁺, Li⁺, Ba⁺⁺, Ca⁺⁺, Mg⁺⁺, Mn⁺⁺, Al⁺⁺⁺, Fe⁺⁺⁺) play in influencing cell survival time in a culture medium. In short-term experiments (20–30 min), cell survival time in a 1% peptone medium is directly related to the valence of the ion employed. Long-term observations (lasting up to five days) in a 1% peptone medium containing lower ion concentrations revealed that the effects on cell-cycle time are not correlated with the valence state of the ion. Comparisons were made among the ionic resistances of strains of T. thermophila, of T. pyriformis sensu stricto, and of two subspecies of T. pigmentosa. Strains within a species are highly correlated in their patterns of ionic response, while marked differences between species occur. The most distinctive group of strains examined came from one of the subspecies (syngen 6) of T. pigmentosa.     

Nature of the transport ATPase-digitalis complex. VI. Purification of and ouabain binding to a highly active cardiac Na+, K+-ATPase

A Na⁺,K⁺-ATPase has been isolated from canine heart with a specific activity as high as 200 μmoles of inorganic phosphate/mg protein/hour. Activity is not due to simple detergent activation since specific ouabain binding (i.e., [Mg⁺⁺,Na⁺,ATP] or [Mg⁺⁺,P_i]-ligand dependent) ranged from 200–450 pmoles/mg protein. Specific ouabain binding activities are up to ten times greater than heretofore reported.     

Effects of calcium ions and quinolinic acid on rat kidney mitochondrial kynurenine aminotransferase

At pH 6.4, rat kidney mitochondrial kynurenine aminotransferase activity is enhanced several-fold by the addition of CaCl₂, apparently because Ca⁺⁺ facilitates the translocation of α-ketoglutarate, one of the substrates, across the mitochondrial inner membrane. Chloride salts or Mg⁺⁺, Mn⁺⁺, Na⁺, K⁺, and NH₄⁺ did not have this effect. At pH 6.8, the enzyme activity was near maximal even without added Ca⁺⁺ but was strongly depressed by either of two calcium chelating agents, quinolinic acid (Q.A.) and ethyleneglycol-bis(β-aminoethyl ether)N,N′-tetraacetic acid (EGTA). These observations support the view that Ca⁺⁺ is involved in regulating kidney mitochondrial translocation of α-ketoglutarate and that the reported interference of polycarboxylate anion translocation by Q.A. $\text{in vivo}$ depends on the ability of that agent to chelate Ca⁺⁺.     

The interaction of Na ions with synthetic polynucleotides

The interaction of Na⁺ with poly A, poly U, poly A·poly U, and Poly A·2 poly U has been investigated by means of potentiometry, by means of potentiometry, by means of a linked-function analysis of its effect on the binding of Mg⁺⁺ ions, and of K⁺ by means of an analysis of its effect on the sedimentation coefficients of the polymers. The last method was found to be inapplicable. The results of the other two methods were found to be consistent, except in the case of poly A where the existence of base stacking, influenced by the binding of Mg⁺⁺, significantly affects the linked-function analysis. The results are also consistent with the effects of the concentration of Na⁺ ions on the thermally induced conformational transitions of poly A·poly U and poly A·2 poly U, and with the extents of “binding” of Na⁺ to DNA measured by equilibrium and by transport methods. The interaction of Na⁺ with polynucleotides appears to be physically quite specific, although its thermodynamic basis is not clear. The extent of binding of Na⁺, Ψ, was found to be independent of the total Na⁺ concentration but a quadratic function of the extent of Mg⁺⁺ binding, θ. In the absence of Mg⁺⁺, Ψ = 0.35–0.38 for poly U, 0.40 for poly A, 0.59 for poly A·poly U, and 0.66 for poly A·2 poly U.     

Conformational changes of membrane-bound (Na+−K+)-ATPase as revealed by antibody inhibition

Summary As different structural states of the (Na⁺–K⁺)-ATPase (EC 3.6.1.3) may lead to a changed reactivity to antibodies, the influence of Na⁺, K⁺, Mg⁺⁺, P_i and ATP on the reaction between highly purified (Na⁺–K⁺)-ATPase and antibodies directed against the membrane-bound enzyme was measured. The antigen antibody reaction was registered by measuring the antibody inhibition of (Na⁺–K⁺)-ATPase activity.In themembrane-bound but not in thesolubilized enzyme four different degrees of antibody inhibition were obtained at equilibrium of the antigen antibody reaction if different combinations of Na⁺, K⁺, Mg⁺⁺ and ATP were present during the incubation with the antibodies. Corresponding to the different degrees of inhibition, different rates of enzyme inhibition were measured. (a) The smallest degree of enzyme inhibition was obtained when (i) only Mg⁺⁺, (ii) Mg⁺⁺ and Na⁺ or (iii) Mg⁺⁺ and K⁺ were present during the antigen antibody reaction. (b) The enzyme activity was inhibited more strongly if Na⁺, Mg⁺⁺ and ATP were present together. (c) It was inhibited even more if only (i) Na⁺, (ii) K⁺, (iii) ATP or both (iv) ATP and Na⁺, (v) ATP and K⁺, (vi) ATP and Mg⁺⁺, or if (vii) no ATP and activating ions were present. (d) The highest degree of antibody inhibition was obtained if Mg⁺⁺, ATP and K⁺ were present together.In the presence of Mg⁺⁺ plus ADP and in the presence of Mg⁺⁺ plus the ATP analog adenylyl (--methylene) diphosphonate, Na⁺ and K⁺ did not influence the degree of antibody inhibition as they did in the presence of Mg⁺⁺ plus ATP. It was further found that the degree of antibody inhibition in the presence of Mg⁺⁺, ATP and K⁺ was affected by the sequence in which K⁺ and ATP were added to the enzyme prior to the addition of the antibodies.It is suggested that by antibody inhibition different conformations of the (Na⁺–K⁺)-ATPase could be detected. These conformations may possibly not occur in the solubilized enzyme and therefore do not seem to be necessarily linked to the intermediary steps of the ATP hydrolysis of the enzyme. The structural changes which are induced by Na⁺ and K⁺ in the presence of Mg⁺⁺ plus ATP are proposed to occur during the Na⁺–K⁺ transport.     

Allelopathic effect of Pluchea lanceolata (Asteraceae) on characteristics of four soils and tomato and mustard growth

The effect of the leachate of the noxious weed Pluchea lanceolata was explored using mustard and tomato seedling growth bioassays of four soil types (sandy loam, clay loam, silty loam, and sand). The objectives of the present study were: 1) to determine how soil chemistry changes after addition of leachate and leaves of the weed; 2) to determine what level of input to the soil does not cause significant differences from those of weed-associated soils under field conditions; and 3) to determine whether soil texture affects bioassay results. Leaf leachates of the weed were added to four soil types in different dilutions, and soils were analyzed for pH, electrical conductivity, organic matter, Cl, PO₄, exchangeable Cu^{+ +}, Zn^{+ +}, Na⁺, K⁺, Mg^{+ +}, and Ca^{+ +}, and total phenolics. These results indicated that the leachates of the weed altered chemical characteristics of each soil type. Concentration of phenolics in treatment of each soil type was dilution-dependent. Leachates were more inhibitory on sandy loam and clay loam than on silty loam and sand. Present study indicated that in allelopathic bioassays, amended soils that are nonsignificantly different from weed-associated soils should be taken. Further, present investigations confirmed the significance of good control soil with nonsignificantly altered chemical characteristics from those of natural soils, as well as soil texture to establish allelopathy of ecological relevance.     

An assessment of the relative effects of adverse physical and chemical properties of sodic soil on the growth and yield of wheat (Triticum aestivum L.)

Two wheat varieties were grown in artificially created sodic soils in pots at a range of sodicity levels (exchangeable sodium percentage (ESP) 15–52), with and without an anionic polyacrylamide soil conditioner (PAM) to stabilise soil aggregates. Increasing sodicity decreased the % water stable aggregates (% WSA) in soil and survival, grain and straw yield of wheat. Plants grown at high sodicity also had higher Na⁺, lower K⁺ and Ca²⁺ concentrations and lower K⁺/Na⁺ ratio in flag leaf sap than plants grown in control (non-sodic) soil. Sodicity had no effect on the concentrations of Cu²⁺, Fe²⁺, Mn²⁺ and Zn²⁺ in grains and straw, but total uptake of these micronutrients was deceased due to lower dry weight of these tissues per plant. At all sodicity levels treatment of sodic soil with PAM increased the % WSA to values greater than in the non-sodic control soil, and slightly lowered ESP. Over the range ESP 15–44 the effects of PAM on wheat grain yield increased as sodicity increased, so that at ESP 44 grain yield in the treatment with PAM was only 25% lower than in the non-sodic control. However at ESP 52 the effects of PAM were smaller, and grain yield was 86% lower than in the control. At this sodicity level the decreases in grain yield due to sodicity and the increases in reponse to treatment of sodic soil with PAM were similar in the two varieties tested. At high sodicity levels (ESP 44 and 52) treatment of sodic soil with PAM decreased the concentration of Na⁺ and increased K⁺ and K⁺/Na⁺ ratio in flag leaf sap. However, at the highest sodicity level (ESP 52), flag leaf Na⁺ concentration remained above the level (100 mol m^-3) at which it has been found to be toxic. Concentrations of Cu²⁺, Fe²⁺, Mn²⁺ and Zn²⁺ in grain and straw were unaffected by PAM. These results suggest that at ESP up to 40–50 adverse physical characteristics are the major cause of low wheat yield in sodic soils, either due to their direct effects in decreasing growth, or their indirect effects in increasing uptake of Na⁺ and decreasing uptake of K⁺. Above ESP 50, roots are less able to exclude Na⁺, even in the presence of improved soil physical conditions, so that at these sodicity levels, both adverse physical and adverse chemical properties contribute to the decreased yield. This revised version was published online in June 2006 with corrections to the Cover Date.     

Plant induced alteration in the rhizosphere and the utilisation of soil heterogeneity

Plant-soil interactions result in a special rhizosphere soil chemistry, differing from that of the bulk soil found only a few mm from the root. The aim of this study was to investigate adaptation mechanisms of herbs growing in acid soils through studying their rhizosphere chemistry in a greenhouse experiment and in a field study. Ten herbs were grown in acid soil (pH 4.2 in the soil solution) in the greenhouse. The concentrations of NO₃ ^-, SO₄ ^2-, phosphates, Ca²⁺, Mg²⁺, Mn²⁺, K⁺, Na⁺, NH₄ ⁺ and pH were analysed in soil solutions obtained by centrifugation. The general pattern found was a depletion of nutrients in the rhizosphere compared with their concentrations in the bulk soil. The pH increase (up to 0.7 units) in the rhizosphere soil appeared to be caused by plant uptake of NO₃ ^- (r²=0.88). The ion concentrations in the soil solution of the rhizosphere were dependent on plant species and biomass increase. Although species with a larger biomass and higher growth rates showed a higher degree of ion depletion (except for Na⁺, SO₄ ^2-) in the rhizosphere, there were also species specific responses. A field study of five herbs at five oak forest sites in Southern Sweden (Scania) was also carried out. In addition to the soil solution concentrations, the loss on ignition (LOI) and the concentrations of 0.1 M BaCl₂ extractable K⁺, Mg²⁺, Mn²⁺, Ca²⁺, and Al ions were measured. The amount of soil solution Al was determined as free ionic (quickly reacting) Al. For all species and sites, the LOI and the concentrations of exchangeable cations were higher in the rhizosphere than in the bulk soil, apparently due to the roots preferably growing at organic-rich microsites. The concentrations of the ions as measured in the centrifuged soil solution, were either higher in the rhizosphere than in the bulk soil or were the same in both, except for NO₃ ^- and quickly reacting Al. The lower concentrations of quickly reacting Al in the rhizosphere, compared with the bulk soil could indicate the uptake of Al by the plant or the exudation of complexing substances. The pH differences were only small and mostly non-significant. Plant-soil interactions and the ability of plants to utilise heterogeneity of the soil appear to be more important for plant growth in acid soils than recognised heretofore. Rhizosphere studies provide an important means of understanding plant strategies in acid soils. This revised version was published online in June 2006 with corrections to the Cover Date.     

Graded and All-or-None Electrogenesis in Arthropod Muscle : I. The effects of alkali-earth cations on the neuromuscular system of Romalea microptera

Graded electrically excited responsiveness of Romalea muscle fibers is converted to all-or-none activity by Ba⁺⁺, Sr⁺⁺, or Ca⁺⁺, the two former being much the more effective in this action. The change occurs with as little as 7 to 10 per cent of Na⁺ substituted by Ba⁺⁺. The spikes now produced have overshoots and may be extremely prolonged, lasting many seconds. During the spike the membrane resistance is lower than in the resting fiber, but the resting resistance and time constant are considerably increased by the alkali-earth ions. The excitability is also increased, spikes arising neurogenically from spontaneous repetitive discharges in the axon as well as myogenically from spontaneous activity in the muscle fibers. Repetitive responses frequently occur on intracellular stimulation with a brief pulse. The data indicate that the alkali-earth ions exert a complex of effects on the different action components of electrically excitable membrane. They may be described in terms of the ionic theory as follows: The resting K⁺ conductance is diminished. The sodium inactivation process is also diminished, and sodium activation may be increased. Together these changes can act to convert graded responsiveness to the all-or-none variety. The alkali-earth ions can also to some degree carry inward positive charge during activity, since spikes are produced when Na⁺ is fully replaced with the divalent ions.     

淋洗与植物作用耦合对盐渍化土壤的改良效应

以甘肃秦王川引大灌区盐渍化土壤为背景,以当地5种耐盐植物为材料,采用根袋法盆栽试验动态研究了淋洗结合植物种植对盐渍化土壤改良的效应。结果表明:与种前相比,单纯的淋洗作用对土壤pH值影响不大,而淋洗结合植物种植明显降低了土壤pH值,且根际土壤pH值小于非根际土壤的,5种耐盐植物中霸王根际土壤pH值降低幅度最大,达0.6个单位。K+、Ca2+、Na+、Mg2+、Cl-和SO2-4在5种植物根际土壤中均有不同程度的富集,富集程度因物种的不同而不同,随培养时间的延长而呈波动状态。5种供试植物和对照组土壤中的6种主要的可溶性盐分离子随淋洗次数和培养时间的延长呈下降趋势。在培养120d后,单纯淋洗的土壤中K+、Ca2+、Na+、Mg2+、Cl-和SO2-4的含量相比种前平均分别降低了33.3%、26.1%、35.6%、32.5%、35.5%和36.3%,植物吸收带走的上述各离子的含量平均分别占种前的46.2%、8.1%、30.2%、7.2%和21.6%,其中霸王吸收带走的盐分离子最多,而淋洗结合种植植物的土壤中上述各离子的含量与种前相比平均分别降低了67.25%、63.73%、83.8%、67.5%、81.55%和78.46%,由此可见,淋洗结合植物种植的脱盐效果优于单纯淋洗,且土壤中主要的盐分离子Na+、Cl-和SO2-4的含量降低幅度最大,通过计算得出,在Cl-、SO2-4和Na+减少的总量中还有37.73%的Na+、38.22%的Cl-和35.14%的SO2-4的减少量是由植物根系的物理化学作用机制引起的。     

Response of sugarcane to different types of salt stress

Summary Due to climatic conditions and prevailing water regime the yield and sucrose recovery in sugarcane are high in South Western India. However, excessive irrigation, poor drainage and luxuriant use of fertilizers have resulted in conversion of large fertile areas into saline lands. The salinity is due to the excess of Na⁺, Ca⁺⁺, Mg⁺⁺, SO₄ ^– and Cl^– ions. Individual salts of NaCl, Na₂SO₄, MgCl₂ and MgSO₄ were employed in culture experiments to study salt stress effect on sugarcane variety Co 740. It was observed that sulphate salinity was more toxic to sugarcane than the chloride one. Sulphate salts caused more inhibition of growth, chlorophyll synthesis, PEPCase activity, decreased the uptake of K⁺ and Ca⁺⁺ ions but stimulated nitrate reductase. The stress did not result in proline accumulation in the sugarcane cultivar Co 740. The degree of toxicity of different ions in decreasing order in sugarcane cultivar Co 740 is SO₄ ^–>Na⁺>Cl^–>Mg⁺⁺.     

Fire and soil-plant nutrient relations in a pine-wiregrass savanna on the coastal plain of North Carolina

Summary Changes in soil and plant nutrient conditions were evaluated following various burn and clip treatments in a longleaf pine-wiregrass savanna in Bladen Co., N.C., USA. Ground fires were found to add substantial quantities of N, P, K, Ca, and Mg to the soil, though not necessarily in forms immediately available to plants. Less than 1% of the total nitrogen in the charred residue (ash) is present as nitrate or ammonium. Considerable quantities of all nutrients examined were lost to the atmosphere during burning. Green leaf tissue in recently burned areas was consistently higher in N, P, K, Ca, and Mg compared to unburned areas. Howerver, when compared to similar tissues from clipped plots, burned area tissues were significantly higher in N, Ca, and Mg only. Data presented here suggest that tissue age significantly affects nutrient content and must be considered in any analysis of tissue nutrient content following burning. Within 4–6 months following fire, burned-area tissue nutrient content decreases to concentrations found in the unburned area. Burning resulted in initial enrichment of available soil nutrients including PO₄, K⁺, Ca⁺⁺, and Mg⁺⁺, however, NO₃ ^-, and NH₄ ⁺ concentrations in burned soil were not significantly different from unbruned soil. Soil and plant nutrient changes in an area burned two years in succession indicate that repeated burning may diminish nutrient availability. Plant response to various nutrient enrichment treatments of the soil indicated that nitrogen is limiting growth in both burned and unburned soils and that burning may alter some factors other than nutrients which may retard plant growth in unburned areas.