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  • 1
    Electronic Resource
    Electronic Resource
    THE PRESSURE PROBE: A Versatile Tool in Plant Cell Physiology (1999)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Plant Physiology and Plant Molecular Biology 50 (1999), S. 447-472 
    Details
    ISSN: 1040-2519
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract This review discusses how the pressure probe has evolved from an instrument for measuring cell turgor and other water relations parameters into a device for sampling the contents of individual higher plant cells in situ in the living plant. Together with a suite of microanalytical techniques it has permitted the mapping of water and solute relations at the resolution of single cells and has the potential to link quantitatively the traditionally separate areas of water relations and metabolism. The development of the probe is outlined and its modification to measure root pressure and xylem tension described. The deployment of the pressure probe to determine and map turgor, hydraulic conductivity, reflection coefficient, cell rheological properties, solute concentrations and enzyme activities at the resolution of single cells is discussed. The controversy surrounding the interpretation of results obtained with the xylem-pressure probe is included. Possible further developments of the probe and applications of single cell sampling are suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.arplant.50.1.447
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  • 2
    Electronic Resource
    Electronic Resource
    Leaf Diffusive Conductance and Tap Root Cell Turgor Pressure of Sugarbeet (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 10 (1987), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. The interrelationships of leaf diffusive conductance, tap root cell turgor pressure and the diameter of the tap root of sugarbeet were studied. The study was conducted on well-watered plants growing in pots under artificial light in the glasshouse. In a typical experiment, on illumination (400 μmol m−2 s−1) leaf conductance increased from 0.6 to 7.4 mm s−1. Cell turgor pressure in the tap root decreased from 0.8 MPa to 0.45 MPa and the root diameter (9.0 cm) contracted by 145μm. Removal of light resulted in the reversal of each of the above parameters to their previous values. Quantitively similar results were obtained when sugar beet plants were uprooted and the response of each of the parameters was measured. The sequence of events however was different. On stimulation by light, changes in leaf diffusive conductance preceded the turgor and root diameter changes (which were simultaneous) by some 15–20min. In contrast, on uprooting the simultaneous changes in root turgor pressure and diameter preceded the changes in leaf conductance. The lag times between changes in diffusive conductance and turgor pressure in the root were between 20 and 30 min.Tap root turgor pressure and diameter correlated strongly and permitted the calculation of an apparent whole root volumetric elastic modules (55–63 MPa). The small changes in tissue volume relative to the transpiration rate suggest that the tap root is not a significant source of transpirational water during the day.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11604755
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  • 3
    Electronic Resource
    Electronic Resource
    Compartmental nitrate concentrations in barley root cells measured with nitrate-selective microelectrodes and by single-cell sap sampling (1991)
    Springer
    Planta 185 (1991), S. 356-361 
    Details
    ISSN: 1432-2048
    Keywords: Hordeum (intracellular nitrate) ; Nitrate compartmentation (cytosol, vacuole) ; Root (intracellular nitrate)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrate-selective microelectrodes were used to measure intracellular nitrate concentrations (as activities) in epidermal and cortical cells of roots of 5-d-old barley (Hordeum vulgare L.) seedlings grown in nutrient solution containing 10 mol · m−3 nitrate. Measurements in each cell type grouped into two populations with mean (±SE) values of 5.4 ± 0.5 mol · m−3 (n=19) and 41.8 ± 2.6 mol · m−3 (n = 35) in epidermal cells, and 3.2 ± 1.2 mol · m−3 (n = 4) and 72.8 ± 8.4 mol · m−3 (n = 13) in cortical cells. These could represent the cytoplasmic and vacuolar nitrate concentrations, respectively, in each cell type. To test this hypothesis, a single-cell sampling procedure was used to withdraw a vacuolar sap sample from individual epidermal and cortical cells. Measurement of the nitrate concentration in these samples by a fluorometric nitrate-reductase assay confirmed a mean vacuolar nitrate concentration of 52.6 ± 5.3 mol · m−3 (n = 10) in epidermal cells and 101.2 ± 4.8 mol · m−3 (n = 44) in cortical cells. The nitrate-reductase assay gave only a single population of measurements in each cell type, supporting the hypothesis that the higher of the two populations of electrode measurements in each cell type are vacuolar in origin. Differences in the absolute values obtained by these methods are probably related to the fact that the nitrate electrodes were calibrated against nitrate activity but the enzymic assay against concentration. Furthermore, a 28-h time course for the accumulation of nitrate measured with electrodes in epidermal cells showed the apparent cytoplasmic measurements remained constant at 5.0 ± 0.7 mol · m−3, while the vacuole accumulated nitrate to 30–50 mol · m−3. The implications of the data for mechanisms of nitrate transport at the plasma membrane and tonoplast are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201056
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  • 4
    Electronic Resource
    Electronic Resource
    Vacuolar solutes in the upper epidermis of barley leaves (1995)
    Springer
    Planta 196 (1995), S. 40-49 
    Details
    ISSN: 1432-2048
    Keywords: Epidermis (leaf) ; Hordeum ; Solute distribution (micro-sampling) ; Stomata ; Vacuole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The concentrations of vacuolar solutes in different cells of the upper epidermis of the third leaf of barley (Hordeum vulgare L.) were studied in leaves of different ages grown under different irradiances (120 or 400 μmol photons·m−2·s−1). Vacuolar saps were extracted from individual cells located at various positions between adjacent veins and were analysed for their osmolality and the concentrations of K+, Ca2+, Cl−, NO 3 − and malate. Each ion showed a cell-specific distribution within the epidermis that was both quantitatively and qualitatively dependent on the leaf developmental stage and on the light level. During leaf ageing, Ca2+ accumulated preferentially in interstomatal cells (i.e. those located between longitudinally adjacent stomata) at concentrations up to 180 mM. Under low light conditions, this was accompanied by a more or less equal decrease in K+ concentration. Epidermal malate was found only in plants grown continuously or transiently under the high irradiance and reached highest concentrations in trough and interstomatal cells (60 to 150mM). Chloride concentration was highest in cells overlying the veins (designated as ridge cells) and lowest in cells located between the veins (trough cells), while NO 3 − exhibited the reverse distribution, although the precise patterns were age-dependent. Epidermal osmolality increased with age, but the intercellular differences in the osmolalities were small compared to differences in vacuolar solute composition. A cell-to-cell analysis of the region surrounding the stomata showed that the steepest changes in the vacuolar solute composition of epidermal cells occurred at the boundary between ridge or trough cells and the adjacent near-stomatal cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00193215
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  • 5
    Electronic Resource
    Electronic Resource
    The regulation of turgor pressure during sucrose mobilisation and salt accumulation by excised storage-root tissue of red beet (1987)
    Springer
    Planta 170 (1987), S. 353-361 
    Details
    ISSN: 1432-2048
    Keywords: Beta (storage root) ; Osmotic pressure ; Salt uptake ; Sucrose mobilisation ; Turgor pressure ; Vacuole (solute content)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The changes in turgor pressure that accompany the mobilisation of sucrose and accumulation of salts by excised disks of storage-root tissue of red beet (Beta vulgaris L.) have been investigated. Disks were washed in solutions containing mannitol until all of their sucrose had disappeared and then were transferred to solutions containing 5 mol·m-3 KCl+5 mol·m-3 NaCl in addition to the mannitol. Changes in solute contents, osmotic pressure and turgor pressure (measured with a pressure probe) were followed. As sucrose disappeared from the tissue, reducing sugars were accumulated. For disks in 200 mol·m-3 mannitol, the final reducing-sugar concentration equalled the initial sucrose concentration so there was no change in osmotic pressure or turgor pressure. At lower mannitol concentrations, there was a decrease in tissue osmotic pressure which was caused by a turgor-driven leakage of solutes. At concentrations of mannitol greater than 200 mol·m-3, osmotic pressure and turgor pressure increased because reducing-sugar accumulation exceeded the initial sucrose concentration. When salts were provided they were absorbed by the tissue and reducing-sugar concentrations fell. This indicated that salts were replacing sugars in the vacuole and releasing them for metabolism. The changes in salf and sugar concentrations were not equal because there was an increase in osmotic pressure and turgor pressure. The amount of salt absorbed was not affected by the external mannitol concentration, indicating that turgor pressure did not affect this process. The implications of the results for the control of turgor pressure during the mobilisation of vacuolar sucrose are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00395027
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of abscisic acid on cell turgor pressures, solute content and growth of wheat roots (1987)
    Springer
    Planta 170 (1987), S. 257-262 
    Details
    ISSN: 1432-2048
    Keywords: Abscisic acid and turgor ; Root growth ; Solute relations ; Triticum (roots) ; Turgor pressure ; Water relations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Abscisic acid (ABA) was shown to influence turgor pressure and growth in wheat (Triticum aestivum L.) roots. At a concentrations of 25 mmol·m-3, ABA increased the turgor pressure of cells located within 1 cm of the tip by up to 450 kPa. At 4 to 5 cm from the root tip this concentration of ABA reduced the turgor pressure of peripheral cells (epidermis and the first few cortical cell layers) to zero or close to zero while that of the inner cells was increased. Increases in sap osmolality were dependent on the concentration of ABA and the effect saturated at 5 mmol·m-3 ABA. The increase in osmolality took about 4 h and was partly the result of reducing-sugar accumulation. Levels of inorganic cations were not affected by ABA. Root growth was inhibited at ABA concentrations that caused a turgor-pressure increase. The results show that while ABA can affect root cell turgor pressures, this effect does not result in increased root growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397896
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  • 7
    Electronic Resource
    Electronic Resource
    Water-relation parameters of epidermal and cortical cells in the primary root ofTriticum aestivum L. (1983)
    Springer
    Planta 158 (1983), S. 230-236 
    Details
    ISSN: 1432-2048
    Keywords: Elastic modulus ; Hydraulic conductivity ; Root (water transport) ; Triticum (water transport) ; Turgor pressure (root) ; Water transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Water-relation parameters of root hair cells, hairless epidermal cells, and cortical cells in the primary root of wheat have been measured using the pressure-probe technique. Under well-watered conditions the mean cell turgor of cortical cells was 6.8±1.9 (30) bar (mean±SD; the number of observations in brackets). In hairless epidermal and root hair cells the mean cell turgor was 5.5±1.9 (22) and 4.4±1.5 (15) bar, respectively. Despite the large variability, turgor pressure was significantly lower (confidence interval=0.95) in epidermal cells relative to cortical cells. This may be a consequence of the ultrafiltration of ions by the external cell wall and-or plasmalemma of epidermal cells. The volumetric elastic modulus of the cells ranged from 10 to 150 bar. This parameter was dependent on cell volume, but within experimental accuracy, was independent of cell type. No pressure dependence of the volumetric elastic modulus was observed in these cells. The half-times for water exchange ranged from 1.8 to 48.8 s. The mean value increased in the order root hair 〈 hairless epidermal 〈 cortical cells and was directly related to volume to surface area ratio. Thus the hydraulic conductivities of the three cell types were similar and averaged 1.2±0.9·10-6 (170) cm s-1 bar-1. No polarity was observed between inwardly and outwardly directed water flow. The similarity of the hydraulic conductivities of root hairs to those of other cells indicates that the membranes of root hairs are not particularly specialized for water transport. The overall hydraulic conductivity for radial water flow across the root was estimated from the pressure-probe data using a simple model and was compared with that measured directly on whole roots using an osmotic backflow technique. It was tentatively concluded that upon sudden osmotic perturbation, the major pathway for water transfer across the root may be through the symplasm and involve net flow from vacuole to vacuole.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01075259
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  • 8
    Electronic Resource
    Electronic Resource
    An attempt to use isolated vacuoles to determine the distribution of sodium and potassium in cells of storage roots of red beet (Beta vulgaris L.) (1983)
    Springer
    Planta 159 (1983), S. 469-475 
    Details
    ISSN: 1432-2048
    Keywords: Beta (ion compartmentation) ; Extracellular space ; Ion compartmentation ; Turgor ; Vacuole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Vacuoles isolated from red beet (Beta vulgaris L.) storage roots contain Na+ and K+ but their analysis does not give reliable information about the size of vacuolar pools of these ions in vivo. Analyses of isolated vacuoles indicated that between 53% and 90% of the Na+ was located in the vacuole and that the vacuolar concentrations of Na+ ranged between 4 and 45 mol m-3. Calculated concentrations of K+ in the vacuoles varied between 32 and 72 mol m-3 but, in contrast to Na+, only about 50% of the K+ was located in the vacuole. Considerations of the likely cytoplasmic concentrations of Na+ and K+ suggest that if these results indicate conditions in vivo a large proportion of these ions must be located in the extracellular space, where they would exert considerable osmotic pressure. To test this, the effect of washing on cell turgor (measured directly with a pressure probe) and on loss of Na+ and K+ was determined. Washing caused an increase in turgor of 5 bar but losses of Na+ and K+ were less than predicted by the experiments with isolated vacuoles. It is concluded that beet vacuoles leak Na+ and K+ when isolated resulting in an underestimation of the size of vacuolar pools of these cations in vivo. Nonetheless, the turgor measurements provide evidence for the presence of osmotically active solute in the extracellular space. The possible contribution of extracellular Na+ and K+ to the observed turgor reduction is calculated and the physiological importance of the accumulation of extracellular solutes is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392083
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  • 9
    Electronic Resource
    Electronic Resource
    The integration of whole-root and cellular hydraulic conductivities in cereal roots (1988)
    Springer
    Planta 174 (1988), S. 1-7 
    Details
    ISSN: 1432-2048
    Keywords: Apoplast ; Hydraulic conductivity ; Root (hydraulic conductivity) ; Symplast ; Triticum (water conductivity) ; Water relations ; Zea (water conductivity)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The hydraulic conductivities of excised whole root systems of wheat (Triticum aestivum L. cv. Atou) and of single excised roots of wheat and maize (Zea mays L. cv. Passat) were measured using an osmotically induced back-flow technique. Ninety minutes after excision the values for single excised roots ranged from 1.6·10-8 to 5.5·10-8 m·s-1·MPa-1 in wheat and from 0.9·10-8 to 4.8·10-8 m·s-1·MPa-1 in maize. The main source of variation was a decrease in the value as root length increased. The hydraulic conductivities of whole root systems, but not of single excised roots, were smaller 15 h after excision. This was not caused by occlusion of the xylem at the cut end of the coleoptile. The hydraulic conductivities of epidermal, cortical and endodermal cells were measured using a pressure probe. Epidermal and cortical cells of both wheat and maize roots gave mean values of 1.2·10-7 m·s-1·MPa-1 but in endodermal cells (measured only in wheat) the mean value was 0.5·10-7 m·s-1·MPa-1. The cellular hydraulic conductivities were used to calculate the root hydraulic conductivities expected if water flow across the root was via transcellular (vacuole-to-vacuole), apoplasmic or symplasmic pathways. The results indicate that, in freshly excised roots, the bulk of water flow is unlikely to be via the transcellular pathway. This is in contrast to our previous conclusion (H. Jones, A.D. Tomos, R.A. Leigh and R.G. Wyn Jones 1983, Planta 158, 230–236) which was based on results obtained with whole root systems of wheat measured 14–15 h after excision and which probably gave artefactually low values for root hydraulic conductivity. It is now concluded that, near the root tip, water flow could be through a symplasmic pathway in which the only substantial resistances to water flow are provided by the outer epidermal and the inner endodermal plasma membranes. Further from the tip, the measured hydraulic conductivities of the roots are consistent with flow either through the symplasmic or apoplasmic pathways.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394866
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  • 10
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    An attempt to use isolated vacuoles to determine the distribution of sodium and potassium in cells of storage roots of red beet (Beta vulgaris L.) (1983)
    Springer
    Details
    Publication Date: 1983-01-01
    Print ISSN: 0032-0935
    Electronic ISSN: 1432-2048
    Topics: Biology
    Published by Springer
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