Mitochondria in fine afferent nerve fibres of the knee joint in the cat: a quantitative electron-microscopical examination

The distribution of mitochondria, their content and concentration (expressed as the ratio of the mean volume of mitochondria and the surface of the sensory axon) were determined in group-III and-IV nerve fibres innervating the knee joint capsule in the cat. Mitochondria mainly accumulated in axonal swellings (beads) and end bulbs of the terminal branches. Between single nerve fibres, marked differences in the content and the concentration of mitochondria were obtained in proximal portions (inside of the perineurium) and in distal portions (unmyelinated sensory endings). In group-III nerve fibres, the mitochondrial concentration ranged from 0.005 to 0.030 m³/m² (proximal portion) and from 0.016 to 0.080 m³/m² (distal portion). In unmyelinated group-IV nerve fibres, the values also showed a broad variation ranging from 0.001 to 0.011 m³/m² (proximal portion) and from 0.003 to 0.019 m³/m² (distal portion). The wide range of mitochondrial concentrations may reflect different energy consumption during receptive processes: nerve fibres with a low mechanical threshold and a high probability of excitatory events may be rich in mitochondria, whereas fibres with a high mechanical threshold and a low probability of excitatory events may be poor in mitochondria.     

The Sertoli cell of the water buffalo (Bubalus bubalis) during the spermatogenic cycle

Summary Ultrastructural features and morphometric evaluations of buffalo Sertoli cells are reported for the six phases of the spermatogenic cycle. The phases of the tubular seminiferous epithelium are identified according to characteristic cellular associations with completed spermiation as demarcation between two cycles. Average tubular diameter (245 m) and epithelial height (61 m) do not vary significantly during the cycle. The relative Sertoli cell volume in the seminiferous epithelium varies between 30% (phase 4) and 39% (phase 8). The calculated volume of a single Sertoli cell increases from a nadir of 7118 m³ in phase 3 abruptly to a maximum of 8968 m³ in phase 4 and is then gradually reduced during the following phases. The Sertoli cell surface area shows a similar trend: it amounts to 11105 m² in phase 3 and to 14260 m² in phase 4. The contact area of the Sertoli cell with adjacent cells and structures is subject to characteristic changes; from the expansion of basal Sertoli-Sertoli contacts it is concluded that the blood-testis barrier in the buffalo is particularly tight during phases 8, 1 and 2. The irregularly contoured nucleus contains a vesicular nucleolus, has a calculated volume from 465 m³ to 543 m³ and occupies 5 to 7% of the cell. Volume percentages of mitochondria (4%), Golgi apparatus and lysosomal bodies are rather constant during the cycle. Whorls and orderly arranged aggregates of the smooth endoplasmic reticulum occur in basal location as well as in close association with elongating spermatids. Smooth ER is the organelle that exhibits the most prominent changes during the Sertoli cell cycle: it occupies 5.79% in phase 3 and 20.9% in phase 4 of the total cellular volume. Phagocytosis of residual bodies is insignificant in this species and a lipid cycle is absent in buffalo Sertoli cells.     

Effect of culture medium ions on chromate reduction by resting cells of Agrobacterium radiobacter

The influence of some ions in pre-growth culture medium on chromate reduction by resting cells of Agrobacterium radiobacter strain EPS-916 was investigated. The reduction was dependent on the Fe²⁺ content of the culture medium: the higher the iron content, the lower the reduction rate. The cells showed maximum chromate reduction when pre-grown in the presence of 0.243 m Mg²⁺, 20 m Ca²⁺ and 3.6 m Mn²⁺. Chromate reduction was not affected by the addition of MgCl₂, CdCl₂, ZnCl₂, MnCl₂, Na₂SO₄ (1000 m), and Na₂MoO₄ (100 m) to the activity assays. However, activity was inhibited by the presence of Na₂SO₄ (10 mm), Na₂MoO₄ (200 m) and ferric citrate.     

Dry to wet weight biomass conversion constant for Tetrahymena elliotti (Ciliophora,Protozoa)

Summary The wet and dry weights of both axenic and monoxenic cultures of the ciliate Tetrahymena were determined directly. These estimates are dependent upon the method of volume determination. Assuming a prolate spheroidal shape for the ciliate, we calculate a mean wet weight of 0.4157±0.0713 pg m^-3 and a mean dry weight of 0.2793±0.0652 pg m^-3. Using electronic cell sizing, our estimates are 0.7869±0.1659 pg m^-3 and 0.5239±0.1101 pg m^-3, respectively. Independent of the method of volume determination, we estimate a mean biomass conversion ratio (dry weight/wet weight) of 0.59±0.08.     

Changes with age in the absorption spectrum of chlorophyll α in a diatom

Summary Absorption spectra of a young and an old culture of the diatom Pheodactylum tricornutum were measured in thin layers between two opal glass sheets. The spectra at 24° and at -196°C were replotted to give equal areas from 730–625 m to allow direct comparison. At 24°C the spectrum for the difference between the two cultures had a negative component of 18 m half width centered at 675 m and a positive region of W_0.5=26 m near 700 m.The spectra at -196°C may be somewhat distorted by clumping of the cells during freezing but nevertheless the 16 day culture clearly showed a smaller proportion of Ca 670 to Ca 680. This older culture has a shoulder due to a 707 m component. The difference curve at -196°C shows the decrease of an unsymmetrical band peaking at 669 m and an increase at 695 m in addition to the 707 m component. Due to the possibility of distortion, the presence of an actual component at 695 is doubtful in these particular cultures.The room temperature spectrum in the chloropyhll a region for the 5 day culture can be closely fitted by a single probability curve at 675 m having a half-width of 31 m. The sum of two components, with widths more reasonable for chlorophylls, also matched the data well enough. These two probability curves, of 22 m half width, centered on 669 and 683.2 m and had a height ratio, h₆₆₉/h₆₈₃ of 1.18. In the 16 day culture the ratio for these bands changed to 1.11 and there was extra absorption around 700 m.Dedicated to Professor C. B. van Niel on the occasion of his 70th birthday     

The susceptibility of the poultry red mite,Dermanyssus gallinae (De Geer, 1778), to some acaricides under laboratory conditions

Toxicity of 14 selected acaricides was tested for a laboratory strain of femaleD. gallinae. The most toxic were carbaryl (LC₅₀=5.0 g/m²), deltamethrin (LC₅₀=7.8 g/m²), bendiocarb (LC₅₀=11.1g/m²), and permethrin (LC₅₀=12.6 g/m²). High level resistance to DDT inD. gallinae was recorded, with factors of resistance at LC₅₀/ LC₉₀ reaching 57/73.     

The quantitative analysis of chromosome pairing and chiasma formation based on the relative frequencies of M I configurations

Whilst reliable estimates of chiasma frequencies can usually not be obtained, the probability (b) of a chromosome arm to be bound by at least one chiasma can often be determined. In the absence of interference this probability equals (1–e ^–2), where 2 is the average chiasma frequency of the chromosome arm and the average crossover frequency or map length. In the presence of interference is shown to retain its genetic meaning as an additive metric that may describe the chromosome arm or other distinctive chromosome segment in terms of genetic recombination. It is a form of potential map length, comparable to, but numerically different from the regular map length. It is termed provisionally crossing-over potential.A chromosome with armsm andn with crossing-over potentials and will form ring bivalents with a frequency (1–e ^–2).(1–e ^–2); open bivalents with a frequency (1–e ^–2).e ^–2+(1–e ^–2).e ^–2; univalent pairs with a frequencye ^–2.e ^–2. Estimates of these frequencies yield equations from which and may be solved. In rye (Secale cereale) their ratio (q) is approximately two and differs from the mitotic arm length ratio of 1.4, indicating localization of chiasmata in the long arms.Graphs are given to show how, with constantq, the relation between the probabilitiesb _m andb _n of the two arms being bound changes with changing averageb.Data are presented on chiasma frequencies in M I, and compared with the frequencies expected in the absence of interference to give an impression of the degree of interference. Apparent fusion of chiasmata simulates interference.     

The Biogeochemical Cycle of Methane in the Coastal Zone and Littoral of the Kandalaksha Bay of the White Sea

Microbiological and biogeochemical investigations of the processes of methane production (MP) and methane oxidation (MO) in the coastal waters and littoral of the Kandalaksha Bay of the White Sea were carried out. The studies were conducted in the coastal zones and in the water areas of the Kandalaksha Preserve, Moscow State University White Sea Biological Station, and the Zoological Institute (RAS) biological station in August 1999, 2000, and 2001 and in March 2001. The rate of CO₂ assimilation in the shallow and littoral sediments was 35–27800 g C/(dm³ day) in summer and 32.8–88.9 g C/(dm³ day) in winter. The maximal rates of MP were observed in the littoral sediments in the zone of macrophyte decomposition, in local depressions, and in the estuary of a freshwater creek (up to 113 l/(dm³ day)). The maximal level of MO was observed in the shallow estuarine sediments (up to 2450 l/(dm³ day)). During the winter season, at the temperature of –0.5 to 0.5°C, the MP rate in the littoral sediments was 0.02–0.3 l/(dm³ day), while the MO rate was 0.06–0.7 l/(dm³ day). The isotopic data obtained indicate that the C_org of the mats and of the upper sediment layers is enriched with the heavy ¹³C isotope by 1–4 as compared to the C_org of the suspension. A striking difference was found between the levels of methane emission by the typical littoral microlandscapes. In fine sediments, the average emission was 675 l CH₄/(m² day); in stormy discharge stretch sediments, it was 1670 l CH₄/(m² day); and under stones and in silted pits, 1370 l CH₄/(m²day). The calculation, performed with consideration of the microlandscape areas with a high production, allowed the CH₄ production of 1 km² of the littoral to be estimated as 192–300 l CH₄/(km² day).     

Factors influencing shoot regeneration from cotyledonary explants ofCucumis melo

Cotyledonary explants of 4-day-oldCucumis melo cv. Hale's Best Jumbo in vitro seedlings showed maximum initiation of shoot buds when cultured onto a revised Murashige & Skoog medium supplemented with 5 M indole-3-acetic acid and 5 M benzylaminopurine and cultured at 25–29°C under low light intensity (5–30 mol m^-2 s^-1). Subculture of the shoot buds onto the same medium without auxin and supplemented with 3 M benzylaminopurine caused the development of shoots from 30% of the buds. The presence of abscisic acid significantly increased the number of explants producing shoot buds. Bud initiation was affected by genotype, seedling age, light intensity, and temperature. Addition of gibberellic acid, thidiazuron or silver nitrate to regeneration medium did not improve either bud initiation or shoot regeneration.     

Three-dimensional organization of smooth muscle cells in blood vessels of laboratory rodents

Summary Three-dimensional aspects of smooth muscle cells of the microvas-culature were studied ultrastructurally in laboratory rodents by means of serial thin sections and reconstruction of muscle cell models. It was demonstrated that a muscle cell of an arteriole (luminal diameter (LD) 17 m) in hamster striated muscle was spindle-shaped, 70 m long, and wound twice round the vessel axis. The volume of the cell was calculated as 750 m³ and its surface area as 1330 m². A muscle cell in an arteriole (LD 6 m) in the rat retina was irregular in shape, about 22 m long, and had branched processes. The cell volume was calculated as 139 m³ and its surface area as 298 m².     

Asymmetric diffusion into the postsynaptic neuron: An extremely efficient mechanism for removing excess GABA from synaptic clefts on the Deiters' neurone plasma membrane

Microdissected Deiters' neuron plasma membranes have been used for studying the passage of GABA through the membrane both in the inward and outward direction. Working with 0.2 mM GABA in the compartment simulating the outside of the neurone and with 2.0 mM GABA in the one simulating the inside we found a net transport of GABA towards the inside. This mechanism does not require a Na⁺ ion gradient across the membrane. The nature of the transport process involved was studied by determining the rate of [³H]-GABA inward passage as a function of GABA concentration (1 nM–800 M) on the outward side of the membrane. The results have shown that until 50 M a diffusion process (v=D₁×C, where D₁=3.1×10^–11 1/m²×sec) is the sole mechanism involved. Above 50 M a second diffusion process is activated v=D₂×(C–50×10^–6), where D₂=2.8×10^–11 1/m²×sec. Taking in account both inward and outward directed diffusion, one can calculate 16 M as the equilibrium concentration of GABA on the outward side of the membrane. From a kinetic point of view, these diffusion processes are able to reduce GABA concentration in a synaptic cleft from 3 mM to 20 M within 3 sec. These diffusion systems are discussed as extremely efficient in removing the excess of released GABA in the synaptic cleft.     

Ecotoxicity of lead to the zebra musselDreissena Polymorpha,Pallas

The effect of lead on the filtration rate of the zebra musselDreissena polymorpha was investigated, together with the accumulation of Pb in the soft tissues of the mussels. The NOEC-filtration was 116 g.l^–1 (0,56 mol.l^–1) and the EC₅₀-filtration was 370 g.l^–1 (1.79 mol.l^–1). The NOEC-accumulation was the concentration found in the control water (1.4g.l^–1). These experiments show that the EC₅₀-filtration for Pb is similar to that for Cd, higher than that for Cu and lower than that for Zn. The water quality criteria for lead allow 25 g Pb.l^–1 in surface water. This will not cause short-term effects. Long-term effects may, however, occur, since an accumulation of Pb as low as 16 g.l^–1 was recorded in this study.     

Characterization of regucalcin effect on proteolytic activity in rat liver cytosol: relation to cysteinyl-proteases

The increasing effect of regucalcin, isolated from rat liver cytosol, on neutral proteolytic activity in the hepatic cytosol was characterized. The proteolytic activity was markedly elevated by the addition of regucalcin (0.1–0.5 M) in the absence of Ca²⁺. This increase was not significantly altered by the presence of diisopropylfluorophsophate (DPF;2.5 mM)—although DFP caused a significant decrease in the proteolytic activity. Regucalcin (0.25 M) additively enhanced the dithiothreitol (DTT; 1.0 mM)—increased proteolytic activity, while the regucalcin or DTT effect was completely abolished by NEM (5 mM), indicating that regucalcin may act on the SH group in proteases. Also, regucalcin (0.25 M) enhanced the effect of Ca²⁺ (10 M) increasing liver proteolytic activity, suggesting that regucalcin does not influence on the active sites for Ca²⁺ in proteases. Moreover, the proteolytic activity of regucalcin (0.25 M) was significantly decreased by the presence of calpastatin (24 g/ml), an inhibitor of Ca²⁺-activated neutral protease (calpain). Now, regucalcin (0.25 M) increased about 7-fold the activity ofm-calpain isolated from rabbit skeletal muscle. These observations demonstrate that regucalcin directly activates cysteinyl-proteases. Regucalcin may have a role as a potent proteolytic activator in the cytoplasm of liver cells.     

Freeze-fracture studies on the cockroach hemocyte membrane complex: Symmetric and asymmetric membrane particle distributions

Summary Freeze-fracture studies were conducted on the membranes of normal cockroach hemocytes. The plasmalemma is asymmetric with the A fracture face containing 80–100 Å membrane intercalated particles at a concentration of 2500/². The B fracture face contains 120–150 Å particles with a relatively low density (800/²). The nuclear envelope displays an asymmetry with the A fracture face containing 1500 particles/² and the B face containing 300/ ². No significant particle size differences were observed in nuclear envelope fracture faces. Two types of symmetric membranes were also found in these cells. Both A and B fracture faces of the membrane surrounding the numerous cytoplasmic inclusion bodies contain particle sizes and concentrations similar to the B face of the plasmalemma. A second type of symmetry was observed in cells apparently engaged in exocytosis. Vesicles (0.1 D) from this process were completely particle free on both fracture faces. Such particle free vesicles could be found in the cytoplasm, attached to the plasmalemma, or completely separated from the cell.Supported by a Pharmaceutical Manufacturers Association Foundation Fellowship.The author wishes to thank Ms. Annalena K. Charla for assistance in plate preparation, Dr. Julius Schultz and the Papanicolaou Cancer Research Institute for use of the freeze-etch device, and Dr. David Smith for the electron microscope facilities.     

Sisal plant regeneration via organogenesis

Callus was initiated from in vitro grown immature leaf and ex vitro grown mature leaf and rhizome explants of Agave sisalana Perr. ex. Engelm, on MS medium containing 2,4-D (9.05 M) and kinetin (4.6 M) or 2,4-D (9.05 M), kinetin (4.6 M) and CH (1000 mg l^–1) or mod. MS (NH₄NO₃, 1500 mg l^–1) containing 2,4-D (9.05 M) and kinetin (4.6 M). Light was essential for callus formation which, however, was different in three types of explants on three different media compositions. Increasing NH₄ ⁺had a negative impact while addition of CH had a positive impact on callus formation. Shoot regeneration from callus from CH-supplemented medium only was achieved for rhizome and immature leaf tissues. The highest rate of regeneration was obtained with BA (26.6 M) as the sole hormone. Shoot buds g^–1 callus varied according to BA concentrations. Shoot proliferation rate increased on half-strength MS medium containing BA (8.9 M). Microshoots developed on MS medium containing BA (2.22 M) and GA₃ (1.44 M) and finally rooted on MS medium containing IAA (11.42 M). Acclimatized rooted plantlets are growing satisfactorily in ex vitro. This is the first report on plant regeneration via organogenesis of A. sisalana.     

Immunohistochemical localization of neuropeptide Y in the guinea pig medulla oblongata

Summary The immunohistochemical localization of neuropeptide Y (NPY) was correlated with those of dopamine--hydroxylase (DBH) and vasoactive intestinal polypeptide (VIP) by mapping serial 7 m paraffin sections at three levels of the guina pig lower brainstem: a) area postrema, b) dorsal motor nucleus of the vagus, and c) nucleus prepositus of the hypoglossal nerve. Based on differences in transmitter expression, three populations of NPY-immunoreactive (IR) neurons were distinguished: NPY-IR catecholaminergic cells (NPY/CA), NPY-IR VIP-ergic cells (NPY/VIP), and NPY-IR cells which were not reactive to either DBH or VIP. Within these populations, size differences among neurons in characteristic locations allowed differentiation among the following subpopulations: NPY/CA neurons in the lateral reticular nucleus — magnocellular part (mean neuronal size 538 m²) and parvocellular part (318 m²)-, in the vagus-solitarius complex (433 m²), and in the dorsal strip (348 m²); NPY/VIP neurons in the vagus-solitarius complex (368 m²) and in the nucleus ovalis (236 m²). Apart from scattered NPY-IR cell bodies in the regions listed above, NPY-IR cell bodies in the lateral portion of the nucleus solitarius and in the caudal part of the spinal nucleus of the trigeminal nerve did not exhibit IR to either DBH or VIP. NPY-IR neurons in the area postrema occurred too infrequently for co-localization studies. The differential distribution of heterogeneous NPY-IR cell subpopulations may reflect the involvement of NPY in a variety of neuronal functions.Supported by the Deutsche Forschungsgemeinschaft, grant He 919/6-1     

Efficiency of photosynthesis in continuous and pulsed light emitting diode irradiation

The light utilization efficiency and relative photon requirement of photosynthesis in pulsed and continuous light from light emitting diodes (LEDs) has been measured. First, we chacterized the photon requirement of photosynthesis from light of LEDs that differ in spectral quality. A photon requirement of 10.3±0.4 was measured using light from a 658 nm peak wavelength (22 nm half band width) LED over the range of 0–50 mol photons m^–2 s^–1 in 2 kPa O₂ in leaves of tomato (Lycopersicon esculentum Mill., cv. VF36). Because the conversion of electrical power to photons increased with wavelength, LED lamps with peak photon output of 668 nm were most efficient for converting electricity to photosynthetically fixed carbon. The effect of pulsed irradiation on photosynthesis was then measured. When all of the light to make the equivalent of 50 mol photons m^–2 s^–1 was provided during 1.5 s pulses of 5000 mol photons m^–2 s^–1 followed by 148.5 s dark periods, photosynthesis was the same as in continuous 50 mol photons m^–2 s^–1. When the pulse light and dark periods were lengthened to 200 s and 19.8 ms, respectively, photosynthesis was reduced, although the averaged photon flux density was unchanged. Under these conditions, the light pulses delivered 10¹⁷ photons m^–2, which we calculate to be equivalent to the capacitance of PS I or PS II. Data support the theory that photons in pulses of 100 s or shorter are absorbed and stored in the reaction centers to be used in electron transport during the dark period. When light/dark pulses were lengthened to 2 ms light and 198 ms dark, net photosynthesis was reduced to half of that measured in continuous light. Pigments of the xanthophyll cycle were not affected by any of these pulsed light treatments even though zeaxanthin formation occurred when leaves were forced to dissipate an equal amount of continuous light.Abbreviations CWF cool white fluorescent - EPS xanthophyll epoxidation state - LED light emitting diode - LUE light utilization efficiency - PFD photon flux density - PR photon requirement (for CO₂ fixation) - PS II primary donor in Photosystem II - RPR relative photon requirement     

Stereospecificity and electrogenicity of amino acid transport in Riccia fluitans

In the aquatic liverwort Riccia fluitans, membrane depolarization (_m), change in membrane conductance (g_m), and current-voltage (I-V) characteristics in the presence of different amino acids as well as the uptake of ¹⁴C-labeled amino acids were measured. L-isomers of the tested amino acids generate larger electrical effects (_m, g_m) than D-isomers, and the I-V characteristics show that the positive electrical inward-current of 20 mA m^-2 generated by 0.5 mM D-serine is only about 50% of the current generated by adding 0.5 mM L-serine. Whereas - and -amino acids rapidly depolarize the membrane to the same extend, with -aminobutyric acid (-AB) and dipeptides no significant electrical effects have been measured. The uptake kinetics of ¹⁴C-labeled amino acids display three components: (I) A saturable high-affinity component with K_s-values of 48 M D-alanine, 12 M -aminoisobutyric acid (AIB), 9 M L-alanine, 8 M L-proline, and 6 M L-serine, respectively; (2) an apparently linear low-affinity component, and (3) an also linear but unspecific component at concentrations >20 times the given K_s-value. Uptake of ¹⁴C-labeled AIB can be inhibited competitively by all tested neutral amino acids, the L-isomers being more effective than the D-isomers, as well as by ammonium or methylamine. Vice versa, AIB competitively inhibits uptake of L-serine and L-alanine. It is concluded that an uncharged stereospecific carrier for the investigated amino acids exists in the plasmalemma of Riccia fluitans. Accumulation ratios of about 50 suggest secondary active transport driven by a transmembrane electro-chemical gradient (mainly _m) which is generated by the electrogenic proton pump. It is suggested that this carrier binds to the amino group forming either a charged binary complex with positively charged amines (Felle 1980), or an uncharged complex with -AB or dipeptides, whereas electrogenic transport of - and -amino acids is mediated by a ternary carrier complex, probably charged by a proton.Symbols and Abbreviations _m membrane potential (mV) - E_co equilibrium potential (mV) of the transport system - g_m membrane (slope) conductance (Sm^-2) - g_m change in g_m - I-V curve current-voltage curve - AIB -aminoisobutytric acid - -AB -aminobutyric acid     

Saccharomyces cerevisiae 2-mum DNA. An analysis of the monomer and its multimers by electron microscopy.

Summary The non-tandem inverted duplication in the 2-m DNA of Saccharomyces cerevisiae has a length of 0.19 m and is located asymmetrically along the molecule. The majority of the dumb-bell structures that are formed upon denaturation and selfannealing of the 2-m monomer consists of the renatured inverted duplication sequences as double stranded stem and two single stranded loops of 0.67 m±0.06 m (S-loop) and 0.86 m±0.05 m (L-loop) length. Two additional size classes which comprised 5–10% of the measured molecules had contour lengths of around 1.7 m and 2.1 m. The smaller dumb-bells contained two S-loops and the larger dumb-bells contained two L-loops as was shown by heteroduplex mapping with an HindIII fragment from the L-loop. Two models which assume illegitimate or site specific recombination, are presented to explain the generation of double S-loop and double L-loop molecules. At least part of the 4-m and 6- circular molecules present in the yeast supercoiled DNA fraction are shown to be dimers and trimers of 2-m monomers, but often with inverted loop segments most probably due to intramolecular recombination between sequences of the inverted duplication.2-m DNA is used to indicate the supercoiled DNA fraction although in our measurements the average monomeric length is 1.9 mPart of this work has been presented at the Conference: The Genetics and Biogenesis of Chloroplasts and Mitochondria, Munich, August, 1976     

Osmotic measurements on stomatal cells ofCommelina communis L.

Summary Observations of aperture changes as sucrose is added to the solution bathing epidermal strips ofCommelina communis L. allow calculation of the osmotic changes required to open or close the stomatal pore, for comparison with changes in potassium content. With isolated guard cells, in strips in which all cells other than guard cells have been killed, the internal osmotic changes required are 83 mosmol kg^–1 m^–1 below 10m aperture, 129 mosmol kg^–1 m^–1 in the range 10–15 m, and 180 mosmol kg^–1 m^–1 above 15 m. For opening against subsidiary cell turgor in addition to guard cell turgor, in intact strips with live subsidiary and epidermal cells, these figures should each be increased by about 33 mosmol kg^–1 m^–1. A change in subsidiary cell turgor is magnified in its effects on the water relations of the guard cell by a factor greater than 3.7 for equal changes in the water potential of the two cells, or greater than 4.7 at constant volume of the guard cell.