Water relations of immobilized giant algal cells

Cells of Halicystis parvula, Acetabularia mediterranea, and Valonia utricularis were immobilized in a cross-linked alginate matrix (4–6% w/w) in order to simulate water-relation experiments in individual cells of higher plant tissues. The immobilization of these cells did not lead to an increase in the mechanical stability of the cell walls. This was demonstrated by measuring the volumetric elastic modulus of the cell wall and its dependence on turgor pressure with the aid of the non-miniaturized pressure probe. In immobilized cells, no changes in the absolute value of the elastic modulus of the cell wall could be detected for any given pressure. At the maximum turgor pressure at which non-immobilized cells normally burst (about 3–7 bar for V. utricularis; depending on cell size, 3 bar for A. mediterranea and 0.9 bar for H. parvula) reversible decreases in the pressure are observed which are succeeded by corresponding pressure increases. This obvervation indicates that coating the cells with the cross-linked matrix protects them from rapid water and turgor pressure loss. Turgor pressure relaxation processes in immobilized cells, which could be induced hydrostatically by means of the pressure probe, yielded accurate values for the half-times of water exchange and for the hydraulic conductivity of the cell membrane. The results demonstrate that the water transport equations derived for single cells in a large surrouding medium are valid for immobilized cells, so that any influence exerted by the unstirred layer which is caused by the presence of the cross-linked matrix can be ignored in the calculations. On the other hand, the evaluation of the half-times of water exchange and the hydraulic conductivity from turgor pressure relaxation processes, which have been induced osmotically, only yields correct values under certain circumstances. The model experiments presented here show, therefore, that the correct Lp-value for an individual cell in a higher plant tissue can probably only be obtained presently by using the pressure probe technique rather than the osmotic method. The results are also discussed in relation to the possible applications of immobilized cells and particularly of immobilized micro-organisms in catalytic reaction runs on an industrial scale.     

Force velocity relations of single cardiac muscle cells: calcium dependency

Cellular cardiac preparations in which spontaneous activity was suppressed by EGTA buffering were isolated by microdissection. Uniform and reproducible contractions were induced by iontophoretically released calcium ions. No effects of a diffusional barrier to calcium ions between the micropipette and the contractile system were detected since the sensitivity of the mechanical performance for calcium was the same regardless of whether a constant amount of calcium ions was released from a single micropipette or from two micropipettes positioned at different sites along the longitudinal axis of the preparation. Force development, muscle length, and shortening velocity of eitherisometric or isotopic contractions were measured simultaneously. Initial length, and hence preload of the preparation were established by means of an electronic stop and any additional load was sensed as afterload. Mechanical performance was derived from force velocity relations and from the interrelationship between simultaneously measured force, length, and shortening velocity. From phase plane analysis of shortening velocity vs, instantaneous length during shortening and from load clamp experiments, the interrelationship between force, shortening, and velocity was shown to be independent of time during the major portion of shortening. Moreover, peak force, shortening, and velocity of shortening depended on the amount of calcium ions in the medium at low and high ionic strength.     

Water relations of the epidermal bladder cells ofOxalis carnosa Molina

All of the cells of the upper (adaxial) epidermis of the leaves ofOxalis carnosa are transformed into large bladders, while in the lower epidermis the bladder cells are interrupted by “normal” cells with stomata. The epidermal bladders contain a high concentration of free oxalic acid (pH approx. 1). Water-relations parameters of these epidermal bladder cells have been determined using the pressure probe. Original cell turgor (P₀) of the closely packed bladders of theupper epidermis was P₀=0.7 to 2.9 bar ( \(\overline {P_0 } = 1.7 \pm 0.5 bar\) ; mean±SD;N=25 cells) and lower than that in the club-shaped bladders of thelower epidermis (P₀=1.3 to 3.7 bar; \(\overline {P_0 } = 2.5 \pm 0.7 bar\) ;N=25 cells). Large differences in the elastic modulus (ε) and the hydraulic conductivity (Lp) of the two different types of cells were observed. For the lower epidermal bladders, ε=18 to 166 bar and was similar to that of other higher plant cells. Also, for these cells it was found that ε was increasing with both, cell turgor and cell volume. By contrast, ε of the cells of the upper epidermis was by one order of magnitude smaller (ε=1.9 to 17.0 bar) and no dependence of ε on cell volume could be detected. The Lp values of the cell membranes were also different (lower epidermis: \(\overline {Lp} = (2.3 \pm 1.6) \cdot 10^{ - 5} cm s^{ - 1} bar^{ - 1}\) ; upper epidermis: \(\overline {Lp} = (3.8 \pm 2.4) \cdot 10^{ - 6} cm s^{ - 1} bar^{ - 1}\) ). These differences seem to be too large to be caused by errors in determining the exchange area for water (A) between cells and adjacent tissue. The half-times of water exchange between bladders and leaf (T_1/2) were, on average, somewhat longer for the upper than for the lower epidermis (lower epidermis: T_1/2=7 to 38 s; upper epidermis: T_1/2=22 to 213 s), but the differences in the T_1/2 values were not as distinct as for ε and Lp. This is because of the compensatory effects of ε, Lp and the different ratios of volume to exchange area. Since the bladders make up about 75% of the entire volume of the leaf, it is assumed that the rate of response of the leaf to changes in the water potential should be similar to that of the bladder cells. The results are discussed in terms of a possible function of the bladders in the leaf.     

Water relations in germinating seeds

Life strategy of plants depends on successful seed germination in the available environment, and sufficient soil water is the most important external factor. Taking into account a broad spectrum of roles played by water in seed viability and its maintenance during germination, the review embraces early germination events in seeds different in their water status. Two seed types are compared, namely orthodox and recalcitrant seeds, in terms of water content in the embryonic axes, vacuole biogenesis, and participation of water channels in membrane water transport. Mature orthodox seeds desiccate to low water content and remain viable during storage, whereas mature recalcitrant seeds are shed while well hydrated but die during desiccation and cannot be stored. In orthodox Vicia faba minor air-dry seeds remaining viable at 8–10% water content in embryonic axes, the vacuoles in hypocotyl are preserved as protein storage vacuoles, then restored to vacuoles in imbibing seeds in the course of protein mobilization. However, in newly produced meristematic root cells, the vacuoles are formed de novo from provacuoles. In recalcitrant Aesculus hippocastanum seeds, embryonic axes have a water content of 63–64% at shedding and they lack protein storage vacuoles but preserve vacuoles preformed in maturing seeds. Independent of the vacuolar biogenetic patterns, their further trend is similar; they expand and fuse, thus producing an osmotic compartment, which precedes and becomes an obligatory step for the initiation of cell elongation. Prior to this, water moves in imbibing seeds through the membranes by diffusion, although the aquaporins forming water channels are present. In both seed types, water channels are opened and actively participate in water transport only after growth initiation. Aquaporin gene expression and their composition change in broad bean embryonic axes after growth initiation. This is the way how a mass water flow into growing seedling cells is achieved, independent of differences in seed water content and vacuole biogenesis patterns.     

Water relations in plants dominating phryganic ecosystems

The water potential and the osmotic potential in plants which dominate Greek phryganic ecosystems (Phlomis fruticosa, Sarcopoterium spinosum, Gistus sp.) were measured from April to Nowember. Water potential decreased considerably reaching a minimum in September. Higher values of osmotic potential than that of water potential were found during dry period (i.e. negative values of pressure potential). This interesting fact was confirmed by artificial desiccation.     

Water relations in grapevine micro-cuttings grownin vitro

Dry mater, water content, water, osmotic and pressure potentials, content of saccharides and potassium were measured duringin vitro cultivation ofVitis rootstocks. Three cases were compared: a) the micro-cuttings with normal growth; b) micro-cuttings which stop their growth after 15 d of culture, and c) micro-cuttings reactivated by 6 d of continuous darkness. Major differences were observed in water content and osmotic potential. The stopping of growth was not a specific property of buds, but was probably due to restriction of translocation of saccharides and water in the shoot.     

Sarcomere distribution patterns in single cardiac cells.

Sarcomeres of single cardiac cells isolated either by microdissection or by enzymatic dissociation were visualized on a television screen, through the objective (63 X) of an inverted microscope and a television camera. A distinct line of the television picture was positioned on the preparation and the frequency content, corresponding to the dark and light areas of the striations was tracked by a phase-locked loop. This technique permitted the measurement of the length of successive sarcomeres and hence the sarcomere distribution pattern over the entire preparation.     

Polarization of fluorescein fluorescence in single cells.

Measurement of fluorescence polarization (P) gives information about the immediate environment of the fluorescent molecule. We used a flow polarimeter to investigate the factors influencing P of fluorescein in mammalian cells to determine whether such measurements are useful for characterizing heterogeneous cell populations. Fluorescein was introduced into cells by incubation with FDA. Measurements of the intensity of fluorescence (TI) and polarization (P) revealed an unexpected dependence: P decreased with increasing intensity of fluorescence. This may be accounted for by the classical model of the binding of small molecules to protein in which P is dependent on the ratio bound to unbound molecules. We have been able to estimate the quenching due to binding and construct a Scatchard plot. We estimated a wavelength shift from in vitro data consistent with the dependence of P on wavelength seen in our cell work. Generally, the distributions of P are symmetrical. Photon statistics broadens the P distribution of dim cells. However, structure does develop in the P distribution when the cells are deprived of calcium or incubated in the cold. This appears as a shoulder on the P distribution or resolves into two peaks. Calcium deprivation may differentially affect a subpopulation of cells whose significance remains to be explored in various cell types.     

Input-output relations in computer-simulated nerve cells

Summary This communication examines, in digital computer simulated networks, the input-output relation established at synaptic level. It is restricted to excitatory junctions and analyzes the changes in post-synaptic discharge which occur when the number of pre-synaptic terminals increases while the EPSP size decreases, when the statistical structure or form (as measured by the interspike interval mean, standard deviation, histogram and by the autocorrelogram) of the spike train in each pre-synaptic fiber changes, and/or when the interdependence between pre-synaptic fibers varies from complete independence to strong dependence.1Independent Pre-synaptic Terminals. When the number of pre-synaptic terminals increases and the EPSP size decreases proportionally (while the input form remains constant), the post-synaptic interspike interval mean increases slightly, the standard deviation decreases markedly, the histogram becomes sharp and narrow and the autocorrelogram becomes periodic. When, on the other hand, the pre-synaptic form varies (while the number of terminals and the EPSP size remain constant), the effect upon the post-synaptio output depends upon the given number of terminals and EPSP size. If terminals are few and EPSP's large, the output varies with the pre-synaptic form. The post-synaptic coefficient of variation is linearly related to the pre-synaptic coefficient of variation, the slope decreasing as the number of inputs increases. If terminals are numerous and weak, the pre-synaptic form ceases to be influential and the post-synaptic cell generates the same output regardless of the detailed structure of the corresponding input. The output common to any combination of independent weak input forms is a very regular train of evenly spaced spikes. (This conclusion is valid unless pre-synaptic terminals fire at extremely low rates.) Such results are mathematically predictable in a simple and realistic model of membrane potential and threshold dynamics (see Appendix).As the EPSP size increases, all other variables being equal, the post-synaptic interval mean decreases monotonically. The decrease is smooth or in steps depending on whether the pre-synaptic form is Poisson or pacemaker, respectively. Post-synaptic spikes are effectively blocked by relatively small numbers of inhibitory terminals.2Dependent Pre-synaptic Terminals. When there is a physiological amount of interdependence between the presynaptic terminals that impinge upon the post-synaptic cell, the activity of the latter is a function of the statistical form of the input channels, even when the latter are numerous and weak. This happens when interdependence involves only a proportion of all terminals or only the terminals within separate and independent groups.In order to understand the transactions that take place in the nervous system, it is necessary to identify the presynaptic statistics that influence the corresponding post-synaptic discharge. When pre-synaptic terminals produce large PSP's their influence is dominant and exerted by way of the precise statistical form of the discharge. When terminals produce small PSP's their influence is contingent on their degree of interdependence. If they are uncorrelated, they act exclusively by way of their mean rates and provide a smooth adjustment of the post-synaptic membrane potential and firing rate. If terminals are correlated, they act by way of several statistical features and assume a dominant role that determines a precise relation between pre-synaptic timing and post-synaptic firing. The degree of inter-terminal correlation is thus a functionally significant variable.

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Zusammenfassung Mit Hilfe eines Digitalrechners wurden die Eingangs-und Ausgangsbeziehungen auf synaptischer Ebene untersucht und dargestellt. Diese Untersuchung erstreckt sich auf erregende Synapsen und analysiert die Veränderungen postsynaptischer Aktionspotentiale, die auftreten, 1. wenn die Anzahl der präsynaptischen axonischen Endigungen ansteigt, während andererseits die Amplitude des EPSP abnimmt; 2. wenn sich die statistische Struktur oder Form der Spike-Kette in jeder präsynaptischen Faser verändert; und/oder 3. wenn die Beziehungen zwischen den präsynaptischen Fasern von völliger Unabhängigkeit bis zu starker Abhängigkeit variiert werden.1Unabhängige präsynaptische Endigungen. Mit zunehmender Anzahl präsynaptischer Endigungen bei gleichzeitiger proportionaler Abnahme des EPSP (Input Form konstant) treten folgende Veränderungen auf: a) das durchschnittliche Intervall zwischen den postsynaptischen Spikes nimmt etwas zu; b) die mittlere statistische Abweichung (standard deviation) nimmt erheblich ab; c) die Form des Histogramms wird eng umschrieben; und d) das Autokorrelogramm nimmt periodischen Charakter an. Wenn andererseits die präsynaptische Form verändert wird (während die Anzahl der Endigungen sowie die Größe des EPSP konstant bleibt), hängt der am postsynaptischen Ausgang registrierte Effekt von der gegebenen Anzahl der Endigungen und von der Größe des EPSP ab. Ist die Anzahl der Endigungen gering und das EPSP groß, dann variiert der Ausgang mit der präsynaptischen Form. Der postsynaptische Variationskoeffizient steht dann in linearer Abhängigkeit vom präsynaptischen Variationskoeffizienten, wobei die Steigung der Geraden mit zunehmendem Eingang abnimmt. Sind die Endigungen zahlreich und die Größen der EPSPs gering, dann übt die präsynaptische Form keinen Einfluß mehr aus, und das von der postsynaptischen Zelle erzeugte Ausgangsprodukt wird unabhängig von der detaillierten Struktur des Eingangs. Für eine jegliche Kombination von unabhängigen und schwachen Eingangsformen stellt sich das Ausgangsprodukt in Form einer sehr regelmäßig gestalteten und durch gleichmäßige Abstände gekennzeichneten Spike-Kette dar (diese Folgerung gilt nur für die Fälle, in denen die präsynaptischen Endigungen sich nicht äußerst langsam entladen). Diese Resultate können mathematisch an Hand eines einfachen Membranmodells abgeleitet werden (s. Appendix).Wenn das EPSP in Größe ansteigt, alle anderen Variablen jedoch gleich bleiben, dann nimmt das postsynaptische Intervall fortwährend ab. Dieser Abfall ist entweder gleichmäßig (präsynaptische Form: Poisson) oder stufenweise (präsynaptische Form: pacemaker). Die postsynaptischen Aktionspotentiale werden durch eine vergleichsweise kleine Anzahl von hemmenden Endigungen wirkungsvoll blockiert.2Abhängige präsynaptische Endigungen. Wenn sich der Grad der Abhängigkeit zwischen den präsynaptischen Endigungen in physiologischen Grenzen bewegt, dann kann die Aktivität der postsynaptischen Zelle als eine Funktion der statistischen Form der Eingangskanäle angegeben werden, und das sogar, wenn die letzteren zahlreich und schwach sind. Dieser Fall tritt dann ein, wenn die Abhängigkeit zwischen den präsynaptischen Endigungen nur einen Teil aller Endigungen oder nur die Endigungen innerhalb getrennter und unabhängiger Gruppen betrifft.Um die im Nervensystem stattfindenden Übertragungen zu verstehen, ist es notwendig, diejenigen präsynaptischen Statistiken zu idendifizieren, die entsprechende postsynaptische Entladungen beeinflussen. Wenn präsynaptische Endigungen große PSPs hervorrufen, dann ist ihr Einfluß dominierend und wird entsprechend der präzisen statistischen Form ausgeübt. Wenn die Endigungen kleine PSPs hervorrufen, dann hängt ihr Einfluß weitgehend von dem Grad der Abhängigkeit voneinander ab. Wenn die präsynaptischen Endigungen unkorreliert sind, dann vermitteln ihre durchschnittlichen, präsynaptischen Entladungsgeschwindigkeiten eine gleichmäßige Regulierung des postsynaptischen Membranpotentials und der postsynaptischen Entladungsgeschwindigkeiten. Sind andererseits die präsynaptischen Endigungen korreliert, dann nehmen sie eine dominierende Funktion ein, und die Beziehungen zwischen präsynaptischer Regulierung und postsynaptischer Entladung können präzise definiert werden. Somit stellt sich der Grad der Abhängigkeit zwischen den präsynaptischen Endigungen als eine funktionell bedeutende Variable dar.

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Supported by a Research Career Program (J. P. S.) and by Grants from the USPHS (NB-02501, NB-05264, NB-07325), and by Air Force Project Rand. Computing assistance was obtained from the UCLA Health Science Computing Facility sponsored by NIH Grant FR-3, and from the Brain Research Institute Data Processing Laboratory.     

Water relations and photosynthesis in Cucumis sativus L. leaves under salt stress

Hydroponically grown cucumber plants were exposed to 14-d period of salinity (0, 50, 100 mM NaCl). NaCl caused reduction in the relative water content in the leaves. The Na⁺ content increased and the K⁺ content decreased. The net photosynthetic rate, stomatal conductance and transpiration rate were markedly decreased by all of the salt treatments. Salinity decreased also the maximum quantum efficiency of photosystem 2 (PS 2) determined as the variable to maximum fluorescence ratio, the photochemical quantum yield of PS 2 and the photochemical fluorescence quenching, while the non-photochemical quenching increased. Above results indicate that NaCl affects photosynthesis through both stomata closure and non-stomatal factors.     

Water relations of compound leaves and phyllodes in Acacia koa var. latifolia

Abstract Moisture release characteristics and field measurements of physiological parameters (conductance and water potential) and environmental parameters (ambient temperature, water vapour saturation deficit and photosynthetic photon flux density) were measured for phyllodes and compound leaves of Acacia koa over a 2 month period at Hawaii Volcanoes National Park, Hawaii, to determine what differences in water relations might occur between leaf types. The phyllodes were found to contain more water at full turgor, use less water in turgor control and have stomatal conductances more closely associated with bulk leaf water status and environmental variables. These results suggest that the phyllodes are more drought adapted, whereas the compound leaves probably promote more rapid early growth during periods of high moisture availability.     

Water relations of the pine exine

BACKGROUND AND AIMS: Water adhesion forces, water absorption capacity and permeability of the pine exine were investigated to consider a possible function of sporopollenin coatings in the control of water transport. METHODS: The experiments were carried out with sporopollenin capsules obtained from pine pollen consisting of an empty central capsule and two sacci. Changes in the concentration of excluded dextran molecules in the medium were analysed to quantify water absorption by purified exine fragments and the osmotic volume flow out of the intact central capsule. KEY RESULTS: The contact angle of sporopollenin to water is higher than the one to ethanol and lower than the one to n-heptane. The water-filled pore space in pine sporopollenin amounts to only 20.6 % of the matrix volume. A monosaccharide was excluded from 15 % and a trisaccharide from about 38 % of this space. Shrinkage of the central capsule induced by permeable osmotica was transient, whereas that induced by sodium polyacrylate (2100 g mol(-1)) was stable. Values obtained for the hydraulic conductance L(P) of the exine (0.39-0.48 microm s(-1) MPa(-1)) are comparable in size to those of biomembranes. Sodium sulfate solutions induced a significant osmotic flow through the exine (reflection coefficient at least 0.6). The exine around the central capsule can be ruptured by equilibration of its lumen with a concentrated electrolyte solution and subsequent transfer to water. The denatured protoplast along with the intact intine was ejected when pollen grains were subjected to this osmotic shock treatment. CONCLUSIONS: The pine exine is easily wetted with water and does not represent a significant barrier to water exchange either liquid or gaseous. Through osmotic burst, it can be separated from the intine. The effect of salts and small solute molecules on water fluxes may be functionally significant for rehydration upon pollination.     

Water relations of fungal spore germination

Summary A simple mathematical model, based on the physiology of spore germination of Penicillium roqueforti and Trichoderma viride TS, is proposed and tested to determine germination kinetics of filamentous fungi. The influence of water and of the nature of the solute used to depress the water activity on conidial germination of these two fungi are discussed. The water activity value of the medium is the main factor but the water molar fraction seems to explain certain observed variations in germination kinetics. The best solutes for germination are those which present the greatest deviation from Raoult's law.     

Water relations of solute accumulation in Pseudomonas fluorescens

When Pseudomonas fluorescens was grown in a glucose salts medium adjusted with NaCl to a water activity (aw) value of 0.980, the intracellular glutamic acid concentration increased 23-fold and comprised 90% of the total amino acid pool. This increase was not observed when the aw of the medium was reduced to 0.980 with sorbitol. Sorbitol was taken up rapidly over a 30 min period and accumulated intracellularly to a level approximately two-fold greater than the concentration in the growth medium. In continuous culture, the specific rate of glutamic acid production and glucose uptake was greater at 0.980 (NaCl) than at 0.997 aw. The maintenance coefficients for glucose uptake were similar at both aw values but were 2.4-fold greater for glutamic acid production at 0.980 (NaCl) than at 0.997 aw.     

Water relations of solute accumulation in Pseudomonas fluorescens

When Pseudomonas fluorescens was grown in a glucose salts medium adjusted with NaCl to a water activity (a_w) value of 0.980, the intracellular glutamic acid concentration increased 23-fold and comprised 90% of the total amino acid pool. This increase was not observed when the a_w of the medium was reduced to 0.980 with sorbitol. Sorbitol was taken up rapidly over a 30 min period and accumulated intracellularly to a level approximately two-fold greater than the concentration in the growth medium. In continuous culture, the specific rate of glutamic acid production and glucose uptake was greater at 0.980 (NaCl) than at 0.997 a_w. The maintenance coefficients for glucose uptake were similar at both a_w values but were 2.4-fold greater for glutamic acid production at 0.980 (NaCl) than at 0.997 a_w.     

Water relations of individual leaf cells ofMesembryanthemum crystallinum plants grown at low and high salinity

Summary The effects of saline conditions on the water relations of cells in intact leaf tissue of the facultative CAM plantMesembryanthemum crystallinum were studied using the pressure probe technique. During a 12-hr light/dark regime a maximum in turgor pressure was recorded for the mesophyll cells of salttreated (CAM) plants at the beginning of the light period followed 6 hr later by a pressure maximum in the bladder cells of the upper epidermis. In contrast, the turgor pressure in the bladder cells of the lower epidermis remained constant during light/dark regime. Turgor pressure maxima were not observed in untreated (C₃) plants.This finding strongly supports the assumption that water movement during malate accumulation and degradation in salttreated plants occurs predominantly between the mesophyll cells and the bladder cells of the upper epidermis. The necessary calculations take differences in the compartment volumes and in the elastic moduli of the cell walls () of the bladder cells of the lower and upper epidermis into account.Measurements of the kinetics of water transport showed that the half-time of water exchange for the two sorts of bladder cells were nearly identical in CAM plants and in C₃ plants. The absolute values of the half-times increased by about 45% in salttreated plants (about 113 sec) compared to the control plants (78 sec). Simultaneously, the half-time of water exchange of the mesophyll cells increased by about 60% from 14 sec (untreated plants) to 22 sec (salt-exposed plants). The leaves of this plant are apparently able to closely maintain the time of propagation of short-term osmotic pressure changes over a large salinity range.A cumulative plot of the data measured on both C₃ and CAM plants showed that the differences between the values of the elastic moduli of bladder cells from the lower and from the upper epidermis are due to differences in volume and suggested that the intrinsic elastic properties of the differently located bladder cells of C₃ and CAM plants were identical.A cumulative plot of the hydraulic conductivity of the membrane obtained both on mesophyll and on bladder cells of salttreated and of untreated plantsvs. the individual turgor pressure yielded a relationship well-known from giant algal cells and some higher plant cells: The hydraulic conductivity increased at very low pressure, indicating that the water permeability properties of the membrane of the various cell types of C₃ and CAM plants are pressure dependent, but otherwise identical.The results suggest that a few fundamental physical relationships control the adaptation of the tissue cells to salinity.     

Water relations in the malonamide-induced haemolysis of mammalian erythrocytes

A revised procedure is described for deriving enthalpy-entropy relations in the haemolysis kinetics of mammalian erythrocytes and its application demonstrates that previously reported linear enthalpy-entropy correlations are statistical artefacts with no real physical basis.Physically valid linear enthalpy-entropy relations do exist between species at constant osmotic concentration, but these are the result of the mutual dependence of the activation parameters on erythrocyte solvent volume. Non-linear enthalpy-entropy dependence on osmotic concentration, which is also physically valid and occurs within species, is attributed to erythrocyte solvent volume variation due to the osmotic properties of haemoglobin.Further development of the data indicates that malonamide-induced haemolysis is essentially an osmotic phenomenon and that the water permeability of all those cells is probably the same.From a consideration of the process in relation to the molecular dynamics of water it appears that the activation enthalpy, entropy and internal energy of haemolysis may refer to the molecular mobility of water during osmosis.