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The freezing points of mixtures of benzene, C6H6, with one of its isotopes, C6D6 and 13C6H6, and those of acetic acid CH3COOH with its isotopes, CH3COOD and CD3COOD, were measured as functions of the molal concentrations of C6D6 and 13C6H6, CH3COOD and CD3COOD, respectively. They changed linearly or non-linearly with increasing molal concentration of C6D6 and 13C6H6, CH3COOD, and CD3COOD, respectively. These findings confirm Kiyosawa’s previous conclusion drawn from experiments on the freezing points of mixtures of H216O with H218O or H217O. This hypothesis states that even a difference in the number of neutrons in the hydrogen or oxygen atoms of water molecules makes water molecules behave as different entities with respect to the colligative properties of solutions. This concept can be extended to mixtures of ordinary benzene with either of its isotopes, C6D6 or 13C6H6, and those of ordinary acetic acid CH3COOH with either of its isotopes, CH3COOD or CD3COOD.

The freezing point of mixtures of H216O with H217O was measured as a function of the molal concentration. The freezing points rose linearly with increasing molal concentration above that of pure ordinary water, H216O, at 273.15 K. This confirms Kiyosawa's previous conclusion [K. Kiyosawa, J. Solution Chem.20, 583 (1991).], drawn from findings on changes in the freezing point of mixtures of H216O with H218O or D216O that even a difference in the number of neutrons in the hydrogen or oxygen atoms of water molecules makes them behave as different entities with respect to the colligative properties of solutions. This has been confirmed to also occur in mixtures of H216O with H217O.

Ca 2+ and P i (inorganic phosphate) releases from isolated calcified and uncalcified Chara cell walls were measured with a Ca 2+ -selective electrode and colorimetry, and their ionic relations were analysed on the basis of the electroneutrality rule. The results showed that (1) not only Ca 2+ but also P i can be released from isolated calcified Chara cell walls into pure deionized water and 100 mM KCI solution, and (2) the positive charge due to the Ca 2+ released cannot be neutralized only by the negative charge from the simultaneously released P i . These findings suggest that calcium bands of calcified Chara cell walls are composed of mainly CaCO 3 and CaHPO 4 and some anions other than P i should be released simultaneously with the Ca 2+ and P i , More Ca 2+ and P i can be solubilized from isolated Chara cell walls in 100 mM KCI solution than in pure deionized water. The pH value of 100 mM KCI solution in which isolated uncalcified young Chara cell walls have been immersed is a little lower than that of pure deionized water in which the same isolated uncalcified young Chara cell walls have been immersed, suggesting that some acidic substances are solubilized by 100 mM KCI. To explain this from the viewpoint of solution chemistry, the solubilities of pure CaCO 3 and pure CaHPO 4 in water and 100 mM KCI solution were measured with a Ca 2+ -selective electrode and their pH values with a glass pH electrode. The conclusion reached was that the Ca 2+ release from isolated Chara cell walls is accompanied by the release of P i , CO 3 2 and acidic substances. This suggests that the so-called calcium bands and or ionic relations, including ion exchange, in Chara cell walls are chemically or physicochemically more complex than they are currently considered to be.

Movements of ions are considered to be governed by the electroneutrality rule. Therefore, a cation moving across the cell membrane into the cell either passively or actively should move together with its counterion, an anion, in equal amounts of charge or in exchange for another cation inside the cell. This means that the net influx of the cation in question should be affected by the permeability of its counterion and/or another cation inside the cell. To examine osmotic and ionic regulation in Chara cells, cell fragments of Chara having a lower osmotic pressure than normal (L-cell fragments) were prepared. The L-cell fragments were individually put into various dilute electrolyte solutions and their osmotic potentials were measured with a turgor balance. Concentrations of K + , Na + , Ca 2+ , Mg 2+ , Cl - , NO 3 - and SO 4 2- in the external electrolyte solutions in which L-cells had been incubated were also analysed by ion chromatography. The results showed that in 0.5 mM KCl + 0.1 mM CaCl 2 solution, Chara L-cell fragments absorbed K + and Cl - to maintain electroneutrality and then regained their osmotic potential very rapidly. When the anion was Cl - , the cation absorbed at the highest rate was K + . On the other hand, when the cation was K + , the anion absorbed at the highest rate was Cl - . Other ions Ca 2+ , SO 4 2- and NO 3 - showed much less permeability than K + and Cl - for the Chara plasma membrane. The conclusion from these findings was that due to the constraint of electroneutral transport, the uptake rate of a salt into L-cells is limited by the permeability of the least permeable ion.

Intact internodal cells of Chara are known to maintain their osmotic pressures at constant levels in artificial pond water at room temperature. Cell fragments with osmotic pressures higher and those cell fragments with osmotic pressures lower than the original, both of which are prepared from intact internodal cells using transcellular osmosis and ligation with threads, can also return their osmotic pressures to the original level within a week in artificial pond water. These regulatory phenomena are realized mainly by extrusion of K + and Cl - in the cytoplasm and/or vacuole or by absorption of K + and Cl - from the external solution

The permeability of internodal cells of Chara australis R. Brown for polyol molecules was determined by using a turgor balance to measure the increase in the osmotic pressure of an internodal cell incubated in artificial pond water containing one of the polyol compounds tested. The permeabilities for ethylene glycol, glycerol, meso-erythritol, xylitol and mannitol were (4. 39 ± 0. 52) × 10−9, (1. 49 ± 0. 40) × 1010, (4. 92 ± 0. 27) × 10−10 (9. 9 ± 3. 4) × 1011 and (7. 6 ± 4. 8) × 10−12 m s−3, respectively. The permeability for glycerol was slightly smaller than that for meso-erythritol, whose molecular weight is larger than that of glycerol in this homologous series: but the reason for this is not clear.

The freezing-point depression and density of aqueous polyol (alditol) solutions were measured, and the osmotic pressure and the partial molar volume of the water of these solutions were calculated. The osmotic pressures calculated from the freezing-point depression data were compared with those calculated with van't Hoff's equation and fairly good agreement was found. The partial molar volumes of the water in the solutions were equal or almost equal to the molar volume of pure water up to the highest concentrations examined. Also, the activity coefficient of the water was unity or almost unity up to the highest concentrations examined.

Freezing-point depression of mixtures of H 2 16 O and H 2 18 O were measured. The results showed that the freezing point of the mixture rose linearly with an increase in the molal concentration of H 2 18 O. The results suggested the formation of a solid solution of H 2 16 O and H 2 18 O by freezing, similar to that formed by H 2 O−D 2 O, and that H 2 18 O behaves as a different molecule than H 2 16 O.

The relationship of molecular volume and maximum molecular radii to the ability of some polyols, ethylene glycol, glycerol and meso -erythritol, to permeate the Chara cell membrane and to the inability of one of the polyols, mannitol, to permeate the Chara cell membrane, was examined by measuring the partial molar volumes of the polyols, V m(2) . Analysis of V m(2) at infinite dilution showed that group additivity is maintained for all the groups, i.e., CH 2 OH and CHOH, of the polyols tested. However, as the permeability and impermeability could not be related to the geometrical properties of the polyol molecules based only on the thermodynamic quantities, molecular models of the polyol molecules were constructed using the CPK(Corey-Pauling Koltum) molecular model, which is designed to have the van der Waals radius of 1Aequivalent to 1.25 cm. The results showed that the maximum radius of the water-filled pore (hydrophilic channel) should be 3.2–3.3A, and the longer the axial length and maximum radius of the polyol molecule, the lesser was its permeative ability. All the experimental and analytical results and inferences support the idea that water molecules pass across the cell membrane through a narrow pore in a single-file fashion.

For survival in adverse environments where there is drought, high salt concentration or low temperature, some plants seem to be able to synthesize biochemical compounds, including proteins, in response to changes in water activity or osmotic pressure. Measurement of the water activity or osmotic pressure of simple aqueous solutions has been based on freezing point depression or vapor pressure deficit. Measurement of the osmotic pressure of plants under water stress has been mainly based on vapor pressure deficit. However, differences have been noted for osmotic pressure values of aqueous polyethylene glycol (PEG) solutions measured by freezing point depression and vapor pressure deficit. For this paper, the physicochemical basis of freezing point depression and vapor pressure deficit were first examined theoretically and then, the osmotic pressure of aqueous ethylene glycol and of PEG solutions were measured by both freezing point depression and vapor pressure deficit in comparison with other aqueous solutions such as NaCl, KCl, CaCl(2), glucose, sucrose, raffinose, and bovine serum albumin (BSA) solutions. The results showed that: (1) freezing point depression and vapor pressure deficit share theoretically the same physicochemical basis; (2) theoretically, they are proportional to the molal concentration of the aqueous solutions to be measured; (3) in practice, the osmotic pressure levels of aqueous NaCl, KCl, CaCl(2), glucose, sucrose, and raffinose solutions increase in proportion to their molal concentrations and there is little inconsistency between those measured by freezing point depression and vapor pressure deficit; (4) the osmotic pressure levels of aqueous ethylene glycol and PEG solutions measured by freezing point depression differed from the values measured by vapor pressure deficit; (5) the osmotic pressure of aqueous BSA solution measured by freezing point depression differed slightly from that measured by vapor pressure deficit.

Precise measurements of the net flux of protons in Chara internodal cells were made with a recently designed high-resolution pH-meter. Survival of intact Chara internodal cells in artificial pond water (APW) that contained HCl at various concentrations was also examined. (...) With reference to the data on the circadian flow of ions in the pulvinus of Phaseolus and ionic regulation in Chara L-cells a discussion is presented of the possibly minor contribution of the net flux of H + in the generation of the electrical membrane potential. Regulation of the net flux of H + in weakly acidic APW is also discussed

A method was developed to enable the determination of the permeability coefficient of theChara cell wall to various solutes from a measurement of the water flow occurring in the solution-cell wall-water system. For this method, the cell wall tube, closed at one end with the natural septum, was connected to a pipette, which serves as a volumeter, by using a glass capillary and a needle.

The osmotic pressures of aqueous saccharide solutions were calculated from the data obtained by means of the freezing-point-depression method. Thus, the water activity and the osmotic pressure of D-glucose, sucrose, and raffinose solutions were measured by the freezing-point-depression method. For dilute aqueous saccharide solutions, the freezing-point depression was proportional to their molal concentrations. However, the higher the molal concentration, the larger the freezing-point depression observed became than those to be expected from the molal concentration dependent on the size of the saccharide molecules. The osmotic pressures calculated from the data of the freezing-point-depression method were compared with those measured with semi-permeable membranes by Morse and his colleagues. To obtain the apparent volumes of hydrated D-glucose, sucrose, and raffinose molecules, their partial molal volumes were measured, together with the partial molal volumes of the water of their solutions. The partial mo...

The mechanism of transcellular osmosis was analyzed on the assumption that the driving force, which is equal to the osmotic pressure of the mannitol solution given to the exosmosis side, is divided into two parts; one causing the inward water flow on the water side, the other causing the outward water flow on the solution side, when each force drives an equal amount of water. Based on this analysis a new procedure was developed to measure the endosmotic and exosmotic water permeabilities of the membranes independently. It involved measurement of volume of water transported transcellularly, change in turgor pressure, and water permeability of the cell wall alone. Experiments following the new procedure revealed that in aNitella internode positioned across a partition wall with equal length both the endosmotic and exosmotic water permeabilities remained constant during transcellular osmosis induced with 0.4M mannitol, at least for the first minute. It was found that the permeability coefficient for endosmosis (3.9 × 10−5 cm sec−1 atm−1) was very much higher than that for exosmosis (1.4× 10−5 cm sec−1 atm−1). Treatment of the endosmotic cell part with 5% ethanol conspicuously decreased the water permeability of the cell on this side down to 1/2.4 the value obtained without ethanol but never affected the permeability on the other side (exosmosis side).

Transport of Rb+ from the roots to the pulvinus and its diurnal movement in the pulvinus were investigated. Rb+ was given to the roots as its chloride or nitrate. The results showed that (1) Rb+ was transported from the roots to the pulvinus through the hypocotyl, epicotyl and petiole, (2) Rb+ was absorbed into the pulvinus in exchange for K+, (3) the absorbed Rb+ moved diurnally in the same phase as the remaining K+. Namely, Rb+ moved in the pulvinus diurnally just like K+.

This study is the first trial to measure the osmotic water permeability or the hydraulic conductivity of the plasmalemma alone of a plant cell. For this purpose tonoplast-free cells were prepared from intenodal cells ofChara australis and their hydraulic conductivities were measured by the transcellular osmosis method.

One of the membrane characteristics of plant cells, rectification, or the direction dependence of water permeability, was investigated inCharaceae internodes using the procedures we developed (Tazawa andKiyosawa 1973) for determining the endosmotic (kpen) and exosmotic (kpex) water permeabilities of the membranes (plasmalemma and tonoplast) in the transcellular osmosis system. Bothkpen andkpex were dependent on the osmotic pressure (πo) of the mannitol solution, which is the driving force for the transcellular osmosis. Thus, kpen increased andkpex decreased with πo. The rectification parameter, or the polarity (ρp), defined askpen/kpex tended to unity when πo approached zero.

The effect of the concentration of the central vacuolar sap on water permeability previously demonstrated onNitella internode (Tazawa and Kamiya 1966), has been further studied. By using a technique of vacuole perfusion the ionic concentration of the cell sap has been modified independently of its tonicity. Transcellular water permeability has been measured by means of a double-chamber osmometer. When the tonicities of artificial saps were adjusted to that of the natural cell sap, wide variations in the concentration of K+, Na+, or Ca++ in the vacuole did not bring about any change in the magnitude of water permeability. On the other hand, water permeability was strongly influenced by varying the tonicity of the vacuolar medium by addition of mannitol. It increased when the tonicity was lowered from the normal level, while it decreased when tonicity was heightened. Water permeability was also decreased by increase in the tonicity of the external medium. Analysis of the results showed that the specific resistance to water flow across the plasmalemma and the tonoplast in series (the reciprocal of the water permeability k′p) was related to the osmotic pressures of the intracellular (π i) and the extracellular (π 0) medium by the empirical formula, l/k′p=0.088 + 0.015 π. + 0.0074π 0. Thus, intra- and extracellular tonicities influence the water permeability of theNitella internode independently of each other. The decrease in water permeability by increase in tonicity of the intra- or extracellular medium may be explained in terms of the effect of these tonicities on hydration of the cell membranes. The water permeability ofLamprothamnium, a brackish water Characeae was only one fourth that ofNitella, a fresh water Characeae. The lower permeability inLamprothamnium may be accounted for in terms of the high tonicities of its cell sap and external medium.

In order to check whether or not the layer of chloroplasts densely arranged in the cortical gel of aNitella internode offers substantial resistance to osmotic water flow, a material was prepared which had the cortical gel layer freed from chloroplasts by centrifugation either longitudinal or lateral to the cell axis. The water permeability of the cell remained the same as normal even though the chloroplasts were exfoliated from the cell cortex to the extent of 50% of the total area, showing that the chloroplast layer plays hardly any significant part as a barrier to osmotic flow. Since it is known that the layer of the streaming endoplasm is also negligible as resistance against osmotic water flow (Tasawa and Kamiya, 1965), it is concluded that the major barrier components against osmotic flow in theNitella internode are the cell wall, plasmalemma and/or tonoplast.

Water permeability of theNitella internode was measured by means of transcellular osmosis. The internode was partitioned into two chambers, one filled with water or alcohol solution and the other with mannitol solution or mannitol-alcohol solution. In this experimental system, the osmotic driving force is equal to the osmotic pressure due to mannitol.