Hydraulic Resistance of Plants. III. Effects of NaCl in Barley and Lupin

1984 ◽  
Vol 11 (5) ◽  
pp. 351 ◽  
Author(s):  
R Munns ◽  
JB Passioura
Keyword(s):  
Osmotic Pressure ◽  
Hydraulic Resistance ◽  
Soil Solution ◽  
Xylem Sap ◽  
External Solution ◽  
White Lupin ◽  
Salt Tolerant ◽  
Osmotic Behaviour ◽  
The Difference ◽  
Shoot Base

Barley (salt-tolerant) and white lupin (salt-sensitive) were grown in sand in pots designed to fit within a pressure chamber. The sand was irrigated with a nutrient solution to which increasing amounts of NaCl were added daily in increments of 10-25 mol m-3. For a range of transpiration rates (Q), the hydrostatic pressure of the leaf xylem sap of an intact plant was measured by applying sufficient air pressure (p) to the root system to raise the pressure of this sap to zero. The relation between p and Q was linear, i.e. of the form p = po + rQ. Po, the intercept on the p axis, reflects the difference in osmotic pressure across the root, and it is assumed that r, the slope of this relation, gives the hydraulic resistance of the plant. In NaCl-treated barley, r remained constant as the NaCl in the soil solution was increased to 200 mol m-3 over 10 days, and differed little from that of the controls. Po increased by about the same amount as the increase in osmotic pressure of the soil solution. This indicates near-perfect osmotic behaviour by the roots, and consistent with this, osmotic pressure of sap expressed from the cut shoot base generally changed little with increasing NaCl, for a given transpiration rate. In NaCl-treated lupin, by contrast, r increased continually from 25 to 150 mol m-3 NaCI, when it was four times that of the controls. Beyond 75 mol m-3, po increased less than increases in the osmotic pressure of the soil solution, which suggests that salts were then leaking into the root xylem. However, the osmotic pressure of the xylem sap flowing through the petiole did not start to increase until 3 days later when the external solution was over 120 mol m-3, suggesting that substantial amounts of NaCl were being removed from the xylem sap before it reached the petiole.

Hydraulic Resistance of Plants. II. Effects of Rooting Medium, and Time of Day, in Barley and Lupin

1984 ◽  
Vol 11 (5) ◽  
pp. 341 ◽  
Author(s):  
JB Passioura ◽  
R Munns
Keyword(s):  
Osmotic Pressure ◽  
Hydraulic Resistance ◽  
External Solution ◽  
Time Of Day ◽  
Pressure Chamber ◽  
Sand Soil ◽  
Rooting Medium ◽  
Wide Range ◽  
Flow Through ◽  
The Difference

Barley and lupin plants were grown in pots designed to fit inside a pressure chamber. The pots contained sand, soil, or nutrient solution. Transpiration rates were varied over a wide range. At a given transpiration rate, Q, the balancing pressure, p, of a plant was determined; p is the pneumatic pressure that must be applied to the roots in the pressure chamber to have a cut in the xylem of the shoot on the verge of bleeding. The relation between p and Q, p(Q), was non-linear and hysteretic for solution- grown plants, but was remarkably linear for plants grown in sand or soil, i.e. the data for a given plant on a given occasion conformed closely to the equation p =po + rQ, where po and r were constants. Even though p(Q) was linear for the plants grown in sand or soil, po was often much larger than Δπ, the difference in osmotic pressure between the external solution and the xylem of the root, so that the apparent hydraulic resistance of the plants, i.e. (p-Δπ)/Q, depended strongly on Q. Furthermore, po changed diurnally and was typically 100-200 kPa higher in the afternoon than in the morning. These results are discussed in relation to the equations that are commonly used to describe water flow through plants. It is postulated that r represents the true hydraulic resistance of the plant, which is independent of Q in the plants grown in soil or sand but may vary diurnally, and that the discrepancy between po and Δπ represents either an additional and hitherto unrecognized difference in osmotic pressure across the membranes of the root that intercept the transpiration stream, or a pressure required to open valves through which the water has to pass, with the valves possibly being located in the plasmodesmata.

scholarly journals THE ACCUMULATION OF ELECTROLYTES

1932 ◽  
Vol 15 (6) ◽  
pp. 667-689 ◽  
Author(s):  
W. J. V. Osterhout ◽  
W. M. Stanley
Keyword(s):  
Steady State ◽  
Osmotic Pressure ◽  
Aqueous Phase ◽  
Thermodynamic Potential ◽  
Ph Value ◽  
Molecular Form ◽  
External Solution ◽  
Aqueous Layer ◽  
The Difference ◽  
Pass Through

Inasmuch as attempts to explain accumulation by the Donnan principle have failed in the case of Valonia, a hypothesis of the steady state has been formulated to explain what occurs. In order to see whether this hypothesis is in harmony with physico-chemical laws attempts have been made to imitate its chief features by means of a model. The model consists of a non-aqueous layer (representing the protoplasmic surface) placed between an alkaline aqueous phase (representing the external solution) and a more acid aqueous phase (representing the cell sap). The model reproduces most of the features of the hypothesis. Attention may be called to the following points. 1. The semipermeable surface is a continuous non-aqueous phase. 2. Potassium penetrates by combining with an acid HX in the non-aqueous layer to form KX which in turn reacts with an acid HA in the sap to form KA. Since KX is little dissociated in the non-aqueous layer potassium appears to pass through it chiefly in molecular form. 3. The internal composition depends on permeability, e.g., sodium penetrates less rapidly than potassium and in consequence potassium predominates over sodium in the "artificial sap." The order of penetration in the model is the same as in Valonia, i.e., K > Na > Ca > Mg, and Cl > SO4, but the quantitative resemblance is not close, e.g., the difference between potassium and sodium, and chloride and sulfate is much less in the model. 4. The formation of KA and NaA in the sap raises its osmotic pressure and water enters. 5. The concentration of potassium and sodium and the osmotic pressure become much greater inside than outside. For example, potassium may become 200 times as concentrated inside as outside. 6. No equilibrium occurs but a steady state is reached in which water and salt enter at the same rate so that the composition of the sap remains constant as its volume increases. 7. Since no equilibrium occurs there is a difference of thermodynamic potential between inside and outside. At the start the thermodynamic potential of KOH is much greater outside than inside. This difference gradually diminishes and in the steady state has about the same value as in Valonia. The difference in pH value between the internal and external solutions is also similar in both cases (about 2 pH units). 8. Accumulation does not depend on the presence of molecules or ions inside which are unable to pass out. One important feature of the hypothesis is not seen in the model: this is the exchange of HCO3 for Cl-. Experiments on this point are in progress.

scholarly journals Uptake of Monosilicic Acid by Trifolium Incarnatum (L.)

1967 ◽  
Vol 20 (2) ◽  
pp. 483 ◽  
Author(s):  
KA Handreck ◽  
LH P Jones
Keyword(s):  
Soil Solution ◽  
Dry Matter ◽  
Xylem Sap ◽  
External Solution ◽  
Avena Sterilis ◽  
Trifolium Incarnatum ◽  
Crimson Clover ◽  
Monosilicic Acid ◽  
Selective Process

Silica is present in soil and culture solutions as undissociated monosilicic acid (H4Si04) and this suggests that its uptake by plants would be a passive, non-selective process. We have earlier reported (Jones and Handreck 1965) that the overall uptake by oats (Avena sterilis cv. Algerian) can be accounted for simply in terms of the concentration of monosilicic acid in the soil solution and the amount of water transpired. Thus, when grown in two potted soils containing 7 and 67 p.p.m. Si02 in solution, oat plants at maturity contained 28 and 274 mg Si02 per plant respectively, having transpired 3�9 litres of water and produced 7�0 g of dry matter. The concentration of silica in xylem sap from oats is similar to that in the external solution. When Trifolium incarnatum (L.) (crimson clover) was grown in these two soils the plants had transpiration ratios of 510-530 but contained silica in concentrations which were only 5-10% of those in oats. This suggests that T. incarnatum has some means of excluding silica from the tops; we have examined this further by measuring the concentration of silica in the xylem sap.

scholarly journals Osmoregulation in some palaemonid prawns

1941 ◽  
Vol 25 (2) ◽  
pp. 317-359 ◽  
Author(s):  
N. Kesava Panikkar
Keyword(s):  
Steady State ◽  
Osmotic Pressure ◽  
Regulatory Mechanism ◽  
Sea Water ◽  
External Medium ◽  
Wide Range ◽  
Osmotic Behaviour ◽  
The Difference ◽  
Slight Rise ◽  
The Individual

1. The brackish-water prawn Palaemonetes varians and the marine prawns Leander serratus and L. squilla are hypotonic in normal sea water, the blood of these species showing osmotic pressures equivalent to 2·3, 2·8 and 2·6 % NaCl respectively, in an external medium of 3·5 % NaCl.2. Palaemonetes varians is isotonic in water of about 2·0 % NaCl and the species is practically homoiosmotic, the difference in its osmotic pressure over a range of 5·0 % NaCl in the external medium being only 0·8–1·0 %. The species has a very wide range of tolerance from water that is nearly fresh to concentrated sea water equivalent to 5·2 % NaCl.3. Leander serratus is much less homoiosmotic than Palaemonetes, and has a limited tolerance to dilution and concentration of the environment. Homoiosmoticity is maintained up to a dilution of 2·5 % in the external medium when isotonicity is reached; but in lower dilutions there is a steady decline in osmotic pressure and the regulatory mechanism evidently breaks down.4. The osmotic behaviour of Leander squilla is very similar to that of L. serratus, but the homoiosmotic behaviour is more marked and it has greater tolerance to dilution of the environment.5. When Leander and Palaemonetes are transferred to very dilute sea water, the internal osmotic pressure falls gradually for about 14–24 hr., varying according to the size of the individual. After the lowest value has been registered there is a slight rise, and a steady state is thereafter maintained.6. Studies on the changes of weight of prawns when transferred to diluted media indicate that the integument (gills) is permeable to water and that, at least in Leander serratus, the amount of water entering is mainly responsible for the dilution of the blood. There is a similar fall in weight when prawns are transferred to concentrated media, due to loss of water.

Effects of nitrogenous materials on translocation and stump exudation in root systems of tomato

1968 ◽  
Vol 46 (4) ◽  
pp. 363-376 ◽  
Author(s):  
Wm. Harold Minshall
Keyword(s):  
Osmotic Pressure ◽  
Time Course ◽  
Xylem Sap ◽  
Potassium Nitrate ◽  
Maximum Effect ◽  
Water Control ◽  
Tomato Plants ◽  
Nitrogenous Compounds ◽  
Average Value ◽  
The Difference

An application of urea or of potassium nitrate to potted tomato plants in the 11- to 18-leaf stage of growth increased markedly the quantity of solutes in the stump exudate for the next 48 to 72 hours. This increase of solutes was most pronounced during the maximum part of the diurnal rhythmic cycle. A large proportion of the increased quantity of solutes was composed of asparagine, glutamine, aspartic acid, glutamic acid, nitrate, ammonium, etc. and thus directly related to the metabolism of the applied nitrogen. In addition, however, increased quantities of phosphorus and, at certain times, of potassium were noted.In detopped tomato plants the increased transfer of solutes from the treatment with nitrogenous materials increased the maximum rate of stump exudation from 2 ml/(plant × hour) for water control plants to 8 ml/(plant × hour). Single plants produced 80 ml of stump exudate in 24 hours. The time course effect on rate of exudation by the two forms of nitrogen differed in that potassium nitrate produced its maximum effect in from 6 to 8 hours following an addition at 0830 hours but urea produced its maximum effect in from 28 to 30 hours. By the fourth day the rate of exudation from nitrogen-treated plants was approximately the same as from water control plants.The Q10 for the rate of exudation of plants treated with nitrogenous compounds varied from 1.6 to 5.2 with an average value of 3.0. As the soil temperature was decreased from 18° to 8 °C the osmotic pressure of the stump exudate increased and the difference was statistically significant at the 1% level. Between soil temperatures of 18° and 28 °C, however, the difference in osmotic pressure of the exudates were not statistically significant. A reduced transport of water by physical means is suggested as the cause of the increase in osmotic pressure of the stump exudate at 8 °C.When plants treated with nitrogenous materials were compared to water control plants no support was found for the theory that active mechanisms participated in the transport of the water. In fact the marked increase in the osmotic pressure of the augmented exudates indicated that a lag existed in the movement of the water.It was concluded that the addition of nitrogenous materials to the soil increased by active processes the movement of solutes into the xylem sap of the plants. By osmosis the increased quantity of solutes then increased the quantity of water transported through the roots and collected as stump exudate.

scholarly journals Methods to Assess Potential Chloride Stress in Citrus: Analysis of Leaves, Fruit, Stem-xylem Sap, and Roots

2005 ◽  
Vol 15 (1) ◽  
pp. 104-108 ◽  
Author(s):  
Eran Raveh
Keyword(s):  
Osmotic Pressure ◽  
Soil Solution ◽  
High Salinity ◽  
Xylem Sap ◽  
Chloride Concentration ◽  
Sampling Time ◽  
Toxic Level ◽  
Leaf Analysis ◽  
High Chloride Concentration ◽  
High Chloride

Chloride stress in commercial citrus is predominantly a result of increased osmotic pressure in the plant as a result of excess chloride. The source of the chloride is usually from the soil solution, where it is absorbed by the roots. After being absorbed, chloride flows through the xylem in the transpiration stream to the shoot, where it is accumulated by transpiring tissues such as leaves and fruit. Monitoring chloride concentration along any of these steps can be used to assess potential stress in the tree. Since some of these tissues tend to accumulate chloride (fruit and leaves) while others do not (root and xylem), analyses should be interpreted within the context of these differences. Having high chloride concentration in roots or xylem-water at a specific sampling time does not necessarily mean that leaves have already accumulated chloride to a toxic level, while having high chloride concentration in fruit or leaf analysis does not necessarily mean that the trees are still being exposed to high salinity in the soil solution. The advantages of the various analyses, as well as their difficulties, are discussed. It was concluded that a combination of xylem sap chloride analysis and leaf chloride analysis are the most useful tools for assessing potential chloride stress in citrus trees.

Capillary pressure, osmotic pressure and bubble contact areas in foams

Soft Matter ◽  
2021 ◽  
Author(s):  
Reinhard Höhler ◽  
Jordan Seknagi ◽  
Andrew Kraynik
Keyword(s):  
Osmotic Pressure ◽  
Capillary Pressure ◽  
Continuous Phase ◽  
Dispersed Phase ◽  
Average Pressure ◽  
Contact Areas ◽  
The Difference

The capillary pressure of foams and emulsions is the difference between the average pressure in the dispersed phase and the pressure in the continuous phase.

Osmotic equilibria in fibroblasts in tissue culture measured by immersion refractometry

1958 ◽  
Vol 149 (934) ◽  
pp. 130-143 ◽  
Keyword(s):  
Water Content ◽  
Osmotic Pressure ◽  
Regression Line ◽  
Fluid Medium ◽  
Physiological Conditions ◽  
Chick Heart ◽  
Osmotic Behaviour ◽  
Osmotic Properties ◽  
Saline Medium

Volume-osmotic pressure relationships at equilibrium have been obtained in chick heart fibroblasts grown in slide-coverslip cultures in a fluid medium consisting of heparinized plasma and embryo extract. The refractive index of the fibroblast gives a direct measure of its solid concentration, and the volume is estimated as the reciprocal of concentration. The volume is found to be linearly related to the reciprocal of the osmotic pressure over a range from 130 to 587 m-osm, provided the measurements are carried out rapidly at 38°C. The isotonic water content of the cells derived from the gradient of the regression line on the basis of the simple Boyle-van’t Hoff Law was found to be less than actual water content obtained by direct refractometry, i. e. the value of Ponder’s ℛ was 0⋅94 (s. d. 0⋅04). In cultures grown in a simple saline medium and measured at 22°C the volume was related linearly to the reciprocal of the osmotic pressure only between the limits of 330 and 191 m-osm. Outside these limits the volume was greater than expected and this was attributed to alterations in the semi-permeable properties of the cell membrane. The value of Ponder’s ℛ in these cultures was 1⋅15. The importance of the quantity, ℛ, as applied to cells other than the erythrocyte, is indicated. The value, 0⋅94 (s. d. 0⋅04), obtained in fibroblasts under physiological conditions is not explicable on the basis of the probable osmotic properties in vitro of the cell proteins. The discrepancy is within the experimental error, but it may also be due to abnormal osmotic behaviour of the cell proteins resulting from some form of intermolecular structure in the cytoplasm.

scholarly journals Testing for ion-mediated enhancement of the hydraulic conductance of the leaf xylem in diverse angiosperms

2017 ◽  
Vol 4 ◽  
pp. e004 ◽  
Author(s):  
Christine Scoffoni ◽  
Grace John ◽  
Herve Cochard ◽  
Lawren Sack
Keyword(s):  
Water Solution ◽  
Pure Water ◽  
Xylem Sap ◽  
Hydraulic Conductance ◽  
Membrane Pores ◽  
Whole Plant ◽  
Pit Membrane ◽  
Major Bottleneck ◽  
The Difference ◽  
Xylem Conduits

Replacing ultra-pure water solution with ion solution closer to the composition of natural xylem sap increases stem hydraulic conductance by up to 58%, likely due to changes in electroviscosity in the pit membrane pores. This effect has been proposed to contribute to the control of plant hydraulic and stomatal conductance and potentially to influence on carbon balance during dehydration. However, this effect has never been directly tested for leaf xylem, which constitutes a major bottleneck in the whole plant. We tested for an ion-mediated increase in the hydraulic conductance of the leaf xylem (Kx) for seven species diverse in phylogeny and drought tolerance. Across species, no significant changes in Kx were observed between 0 and 15 mM KCl. We further tested for an effect of ion solution during measurements of Kx vulnerability to dehydration in Quercus agrifolia and found no significant impact. These results for leaf xylem contrast with the often strong ion effect reported for stems, and we suggest several hypotheses to account for the difference, relating to the structure of xylem conduits across vein orders, and the ultrastructure of leaf xylem pores. A negligible ion response in leaves would weaken xylem sap ion-mediated control of plant hydraulic conductance, facilitating modeling of whole plant hydraulic behavior and its influence on productivity.

Effect of pH on the adsorption of phosphate and potassium in batch and in column experiments

Soil Research ◽  
1988 ◽  
Vol 26 (1) ◽  
pp. 165 ◽  
Author(s):  
NS Bolan ◽  
JK Syers ◽  
RW Tillman
Keyword(s):  
Soil Solution ◽  
Opposite Effect ◽  
Column Experiment ◽  
Batch Experiment ◽  
Column Experiments ◽  
Effect Of Ph ◽  
The Difference

The effect of increasing pH, through incubation with Ca(OH)2 and NaOH, on the adsorption of phosphate (P) and potassium (K) was examined in batch and in column experiments. In column experiments, an increase in pH from 5.2 to 8.2 decreased the adsorption of P and increased that of K which resulted in an increased leaching of P and a decreased leaching of K. In a batch experiment, however, an increase in pH resulting from incubation with NaOH gave similar results to those of the column experiment, whereas an increase in pH due to Ca(OH)2 addition caused the opposite effect on the adsorption of both P and K. The difference between the batch and the column experiments in the effect of incubating soil with Ca(OH)2 on the adsorption of P and K is related to the concentration of Ca in the soil solution.

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