THE ACCUMULATION OF ELECTROLYTES : XI. ACCUMULATION OF NITRATE BY VALONIA AND HALICYSTIS

The nitrate concentration in the sap of Valonia macrophysa, Kütz., is at least 2000 times that of the sea water, and in Halicystis Osterhoutii, Blinks and Blinks, at least 500 times that of the sea water.     

THE ACCUMULATION OF ELECTROLYTES : XII. ACCUMULATION OF HALIDE AND NITRATE BY VALONIA IN HYPERTONIC SOLUTIONS

When cells of Valonia macrophysa were placed in hypertonic sea water, the concentration of halide and of nitrate increased, and the sum of halide + nitrate became 0.05 M greater inside than outside, which is about the same difference as is found in cells in normal sea water. In ordinary sea water the ratio of halide to nitrate is 80,000 to 1. When this was changed by substituting nitrate for halide so that the concentration of halide was 1.75 times that of nitrate the rate of entrance of halide was 1.68 times that of nitrate in 276 hours and the ratio of halide to nitrate in the sap decreased from 38 to 18.5. No halide came out in exchange for entering nitrate. The retention of chloride may well be due to the fact that even when the halide concentration of the sea water is reduced as low as 0.4 M, there is still an inwardly directed activity gradient of sodium chloride.     

THE ACCUMULATION OF ELECTROLYTES : X. ACCUMULATION OF IODINE BY HALICYSTIS AND VALONIA

Analyses of the sap of Halicystis Osterhoutii and of Valonia macrophysa for iodide indicate accumulations of the order of 1000 to 10,000-fold in the first case, and 40 to 250-fold in the second case. The chemical potential of KI, NaI, HI, and CaI₂ is greater inside than outside.     

THE ACCUMULATION OF ELECTROLYTES : II. SUGGESTIONS AS TO THE NATURE OF ACCUMULATION IN VALONIA

It is suggested that K enters chiefly as KOH, whose thermodynamic potential (proportional to the ionic activity product (a _K) (a _OH)) is greater outside than within. As this difference is maintained by the production of acid in the cell K continues to enter, and reaches a greater concentration inside than outside. KOH combines with a weak organic acid which is exchanged for HCl entering from the sea water (or its anion is exchanged for Cl^-), so that KCl accumulates in the sap. Na enters more slowly and its internal concentration remains below that of K. The facts indicate that penetration is chiefly in molecular form. As the system is not in equilibrium the suggestion is not susceptible of thermodynamic proof but it is useful in predicting the behavior of K, Na, and NH₄.     

THE ACCUMULATION OF ELECTROLYTES : I. THE ENTRANCE OF AMMONIA INTO VALONIA MACROPHYSA

When 0.005 M NH₄Cl is added to sea water containing cells of Valonia macrophysa ammonia soon appears in the sap and may reach a concentration inside over 40 times as great as outside. It appears to enter as undissociated NH₃ (or NH₄OH) and tends to reach a pseudoequilibrium in which the activity of undissociated NH₃ (or NH₄OH) is the same inside and outside. When ammonia first enters, the pH value of the sap rapidly rises but it soon reaches a maximum and subsequently falls off. At the same time there is an increase of halide in the sap which, however, does not run a parallel course to the ammonia accumulation, but it comes to a new equilibrium value and remains constant. The increase in NH₃ in the sap is accompanied by a decrease in the concentration of K. As NH₃ enters the specific gravity of the sap decreases and the cells rise to the surface and continue to grow as floating organisms. The growth of the cells is increased.     

THE ACCUMULATION OF ELECTROLYTES : IV. INTERNAL VERSUS EXTERNAL CONCENTRATIONS OF POTASSIUM

Lowering the potassium in the sea water from 0.011 M to 0.006 M caused an exit of potassium from cells of Valonia macrophysa. Sodium continued to penetrate and the ratio K ÷ Na fell off. The cells ceased to grow but there was no evidence of injury. Increasing the external potassium brought about an increase of the internal concentration of potassium, of halide, of total cations, and of the ratio K ÷ Na inside. These phenomena are to be expected on theoretical grounds.     

THE ACCUMULATION OF ELECTROLYTES : VIII. THE ACCUMULATION OF KCl IN MODELS

Models are described in which KCl enters until its chemical potential becomes much greater inside than outside. The energy needed to accomplish this comes from the chemical reactions occurring in the system and the continual supply of certain materials. An important factor is the maintenance of a lower pH value inside by means of CO₂. This may be analogous to what happens in some living cells. The concentration of K⁺ becomes higher inside, as happens in many living cells, but the concentration of Cl^- does not and in this respect the model differs from many living cells. As in Valonia, potassium tends to go out as KCl when the ionic activity product (K)(Cl) is greater inside but at the same time it tends to enter as KOH since the activity product (K)(OH) is greater outside. The net result is entrance of potassium presumably because the latter process is the more rapid.     

SEPARATION OF POTASSIUM ISOTOPES IN VALONIA AND NITELLA

The ratio of K³⁹ ÷ K⁴¹ appears to be lower in the sap of Valonia and Nitella than in the environment, indicating that the living cell can separate these isotopes to some extent. Experiments with a mixture of guaiacol and p-cresol suggest that a similar separation may occur here but further experiments are needed.     

THE ACCUMULATION OF ELECTROLYTES : VII. ORGANIC ELECTROLYTES PART 1

The inorganic constituents of the sap of Rheum (rhubarb), Rumex (field sorrel), and Oxalis (wood sorrel) show a great preponderance of cations over anions, as would be expected if the cations entered chiefly as hydrates (other possibilities will be discussed in Part 2).     

THE ACCUMULATION OF ELECTROLYTES : VII. ORGANIC ELECTROLYTES PART 2

Analyses have been made of the inorganic constituents of the juices expressed from the leaves of Rheum, Rumex, and Oxalis. It has been shown that in all cases there is a large excess of inorganic cations over anions in the sap, the average ratio of cations to anions being 3.8 (Part 1, p. 239). The ash analyses of plant tissues (chiefly leaves) reported in the literature have been examined critically, and it has been shown that the preponderance of inorganic cations over inorganic anions in the ash and in the sap is general. It has been concluded that the excess of inorganic cations is consistent with the view that cations pass into the protoplasm chiefly in the form of hydroxides, and are accumulated either in the form of organic salts (such as the oxalates) or in non-polar linkage. It has been concluded that practically all the potassium and sodium found in plant ash must have been present originally in the form of soluble ionogenic compounds, but that a considerable part of the calcium and magnesium may have been present originally in the form of insoluble salts or as components of non-polar compounds. The methods whereby the cations, particularly potassium, may have been accumulated have been discussed, and it has been concluded that as it does not seem very probable that they enter chiefly as nitrates or bicarbonates we may suppose that they go in to a large extent as hydrates: this is highly probable in the case which has been most carefully investigated (Valonia).     

THE ELECTRICAL CONDUCTIVITY OF SODIUM AND POTASSIUM GUAIACOLATES IN GUAIACOL

The data of the author and Uhlig, and new data, on the conductivity of sodium and of potassium guaiacolates in guaiacol at 25° have been computed with an improved conductance equation which is valid to somewhat higher concentrations than the equations formerly used. The new constants are, Λ₀ = 9.0, K = 2.8 x 10^–5 for sodium guaiacolate and Λ₀ = 9.5, K = 3.4 x 10^–5 for potassium guaiacolate.     

FLUID COMPARTMENTATION AND ELECTROLYTES OF CAT CEREBRAL CORTEX IN VITRO–II SODIUM, POTASSIUM AND CHLORIDE OF MATURE CEREBRAL CORTEX

The contents of K⁺, Na⁺ and Cl^? in various incubation media and in slices of adult cat cerebral cortex incubated in vitro under a variety of conditions have been determined in conjunction with studies on slice swelling and fluid compartmentation reported in the preceding paper (Bourke and Tower , 1966). Cortical slices incubated in media containing 16 Or 27 mm-K⁺ exhibit contents of K⁺ and Na⁺ most nearly comparable to those found in viuo. Substitution of isethionate^? For Cl^? or omission of Ca²⁺ in such media have little effect on slice cation composition. Rb⁺ can effectively substitute for K⁺, but substitution of Li⁺ or choline⁺ for most of the naf in incubation media is associated with accumulation of these cations in slices at the expense of both K⁺ and Na⁺. Compared to values in vivo for net contents and/or concentrations of electrolytes in the non-sucrose spaces of cortical slices, conditions yielding most favourable data in vitro appeared to be incubation of cortical slices in 16 mm -K⁺ medium or in 27 mm -K⁺ medium with either omission of Ca²⁺ or replacement of Cl^? by isethionate. Essentially complete inhibition of maintenance of K⁺ and extrusion of Na⁺ in slices of cat cerebral cortex occurs upon incubation with 10^?5 or 10^?4m -ouabain, with 50 per cent inhibition of cortical slice electrolyte metabolism occurring at about 8 × 10^?7m -ouabain. Cortical slices incubated in 27 mm -K⁺ medium in the presence of ⁴²K exhibited rates of exchange and turnover of slice K⁺ (in non-sucrose spaces) of 0·7 μequiv./min and 6.45 per cent respectively. In the presence of 10^?5m -ouabain, a maximal ratio of slice specific activity/medium specific activity is attained within about 5 min after ⁴²K addition, compared to >20 min for control slices. In neither case does the maximal specific activity ratio exceed about 0.85; this suggests that some 10-15 per cent of total cortical K⁺ comprises a “slowly exchangeable” fraction. In the presence of Ca²⁺ (1.3 mm ) slice oxygen consumption is markedly stimulated (39 per cent) and aerobic glycolysis is markedly depressed (54 per cent) in the presence of 10^?5m -ouabain; whereas on omission of Ca²⁺ from incubation media, both respiration and glycolysis are normally stimulated but, with 10^?5m -ouabain present, both are significantly depressed (20 per cent and 37 per cent respectively). Possible relevance of these effects to mobilization of tissue Ca²⁺ by ouabain and to effects of intracellular Ca²⁺ on mitochondrial respiratory metabolism is discussed.     

THE RELATIONS OF TEMPERATURE TO THE POTASSIUM EFFECT AND THE BIOELECTRIC POTENTIAL OF VALONIA

The effect of temperature upon the bioelectric potential across the protoplasm of impaled Valonia cells is described. Over the ordinary tolerated range, the P.D. is lowest around 25°C., rising both toward 15° and 35°. The time curves are characteristic also. The magnitude of the temperature effect can be controlled by changing the KCl content of the sea water (normally 0.012 M): the magnitude is greatly reduced at 0.006 M KCl, enhanced at 0.024 M, and greatly exaggerated at 0.1 M KCl. Conversely, temperature controls the magnitude of the potassium effect, which is smallest at 25°, with a cusped time course. It is increased, with a smoothly rising course, at 15°, and considerably enhanced, with only a small cusp, at 35°. A temporary "alteration" of the protoplasmic surface by the potassium is suggested to account for the time courses. This alteration does not occur at 15°; the protoplasm recovers only slowly and incompletely at 25°, but rapidly at 35°, in such fashion as to make the P.D. more negative than at 15°. This would account for the temperature effects observed in ordinary sea water.     

THE ACCUMULATION OF ELECTROLYTES : VI. THE EFFECT OF EXTERNAL pH

It would be natural to suppose that potassium enters Valonia as KCl since it appears in this form in the sap. We find, however, that on this basis we cannot predict the behavior of potassium in any respect. But we can readily do so if we assume that it penetrates chiefly as KOH. We may then say that under normal conditions potassium enters the cell because the ionic activity product (K) (OH) is greater outside than inside. This hypothesis.leads to the following predictions: 1. When the product (K) (OH) becomes greater inside (because the inside concentration of OH^- rises, or the outside concentration of K⁺ or of OH^- falls) potassium should leave the cell, though sodium continues to enter. Previous experiments, and those in this paper, indicate that this is the case. 2. Increasing the pH value of the sea water should increase the rate of entrance of potassium, and vice versa. This appears to be shown by the results described in the present paper. It appears that photosynthesis increases the rate of entrance of potassium by increasing the pH value just outside the protoplasm. In darkness there is little or no growth or absorption of electrolytes. The entrance of potassium by ionic exchange (K⁺ exchanged for H⁺ produced in the cell), the ions passing as such through the protoplasmic surface, does not seem to be important.     

DISSIMILARITY OF INNER AND OUTER PROTOPLASMIC SURFACES IN VALONIA. III

Evidence that the inner and outer protoplasmic surfaces in Valonia are unlike is found in the high P.D. across the protoplasm when the external solution has the same composition as the vacuolar sap. Earlier experiments with artificial sap have been repeated, using natural as well as artificial sap. Good agreement between the data with the natural and the artificial solution was found both in the magnitude of the P.D.''s observed and in the shape of the P.D.-time curves. The P.D.''s, however, were considerably higher than the values formerly reported as usual, while the cells proved much less liable to alteration produced by exposure to sap. It is suggested that the cells used in the recent experiments were in a more vigorous condition, perhaps as a result of exposure to stronger illumination. The interpretation of the shape of the P.D.-time curves, proposed in an earlier report, and based on the theory of protoplasmic layers, is further discussed. It is assumed that the fluctuations in P.D. are due to an increase in the concentration of K in the main body of the protoplasm.     

ON GUAIACOL SOLUTIONS : I. THE ELECTRICAL CONDUCTIVITY OF SODIUM AND POTASSIUM GUAIACOLATES IN GUAIACOL

1. Measurements on the densities, viscosities, dielectric constants, and specific conductances of pure anhydrous and water-saturated guaiacol at 25°C. are reported. 2. The solubility of water in guaiacol at 25°C., and its effect on the electrical conductivity of a sodium guaiacolate solution is given. 3. Electrical conductivity measurements are reported on solutions of sodium and potassium guaiacolates in water-saturated guaiacol at 25°C. 4. The decrease of electrical conductivity with increasing concentration for these salts is explained on the basis of an ionic equilibrium combined with the interionic attraction theory of Debye and Hückel. 5. The limiting equivalent conductances of sodium and potassium guaiacolates in water-saturated guaiacol at 25°C., the corresponding limiting ionic mobilities, and the dissociation constants are computed from the conductivity measurements. The salts are found to be weak electrolytes with dissociation constants of the order of 5 x 10^–6.     

九龙江口红树林研究Ⅱ.秋茄群落的钾、钠累积和循环

本文是福建九龙江口红树林生态系统研究的一个部分,主要讨论20年生秋茄群落的钾、钠的含量及其生物循环。试验结果表明:秋茄群落现存量中,含有钾、钠总量分别为531.97和2100.36公斤/公顷;其中地上部分分别为296.49和742.91公斤/公顷;地下部分分别为235.48和1357.45公斤/公顷。该群落钾、钠生物循环中年吸收量分別为109.15和353.50公斤/公顷·年,归还量分别为59.37和160.18公斤/公顷·年。存留量为49.78和193.32公斤/公顷·年。它的钠含量比钾含量大,周转期钾需9年比钠需13年为快。