Suction Tension Research Articles

Thermal analysis of the influence of harmonics on the current capacity of medium‐voltage underground power cables

AbstractIn this article, an algorithm is proposed and used to study the influence of harmonics on the behavior of medium‐voltage underground cables in flat formation. The proposed algorithm is a thermal model based on the heat equilibrium of the thermal circuit nodes of the medium‐voltage cable system. The impact of harmonics on the temperature rise of the cable elements and the cable capacity is evaluated in this article. Also, the impact of harmonics on the derating factors of cable for different soil types is presented. Finally, the measurement of temperatures of cable cores is carried out experimentally and compared with the calculated results to validate the proposed algorithm. One of the algorithm merits is that several harmonic percentages can be taken into account for each cable phase individually, and the heat exchange between the cable phases and their sheath is also taken into consideration. From the obtained results, it is illustrated that the presence of harmonics has a remarkable influence on the cable core temperature; mainly, harmonics of the third and fifth orders may lead to dry zone formation around the cable. It is also observed that the presence of harmonics has an important influence on the cable current, especially when it is buried in soil that has high thermal resistivity during the summer season (suction tension = ∞). In summer, the cable core temperature reached 152.162°C, 139.053°C, and 133.375°C when lime, sand, and silty sand, respectively, are used as backfill materials, rather than 90°C in the normal operating condition of the 11 kV three‐phase single‐core cable. It is observed also that with the increase of the soil thermal resistivity, the ratio of /) reached about 1.2 times at 2.5 K m/W soil thermal resistivity. In addition, it is also observed that the impact of harmonics leads to a percentage reduction in the derating factor of the cable center phase by 11.88%–12.37% depending on the composition of the backfill materials.

Influence of Processing Parameters on Fibre Properties during Twin-Screw Extrusion of Poplar Wood Chips

For sustainable agriculture, the contentious input of peat in growing media needs to be replaced by a substitute with the best possible water-holding capacity (WHC). Wood from fast growing poplar trees, cultivated in short rotation coppices (SRC), is a suitable alternative if it is processed correctly in a twin-screw extruder. The processing parameters, such as the aperture setting of the extruder, moisture content, and specific energy demand (SED), during twin-screw extrusion, as well as their influence on fibre properties such as WHC and particle size distribution, are investigated. SRC-poplar wood chips from clone Max3 are the raw material used for this research. As a result, the best volume-based WHC (75%) at −1 kPa suction tension was achieved for dry extruded wood chip fibre at an aperture setting of 15 mm and an SED of 340 kWh*t−1. The smallest SED of 140 kWh*t−1 was measured at apertures of 35 mm and 40 mm, which resulted in a volume-based WHC of approximately 30% and a dry matter mass flow during processing of 0.289 t*h−1 (40 mm). The particle size distribution of semi-dry wood chips has the highest fine fraction as well as the smallest coarse fraction. Conclusively, poplar wood can be processed fresh and dry into fibre at an acceptable SED, which results in an acceptable WHC.

Research on the Formation Mechanism of Loess Vertical Joints

The popular occurrence of vertical joints in loess formation aggravates the anisotropism of loess and contributes to various geohazards (e.g., slope failures and soil erosion). To alleviate the geohazards caused by the vertical joints, researches need to be carried out to investigate the formation mechanism of these vertical joints. However, the theoretical analysis of the vertical joints’ formation mechanism is limited up to now. In this study, we conducted a laboratory column experiment to observe joint development. Furthermore, using the unsaturated soil theory, we proposed a theoretical model to investigate the tensile stress that contributes to the formation of the loess vertical joint. In the experiment, the air-dried and crushed soil was sifted into the column, which simulates the free fall deposition process of the natural loess in China and contributes to a uniform state. 2500 ml of water was added at the top of the column. The topsoil experienced a wetting-drying process. During desaturation, 9 similar vertical joints were developed with similar horizontal distance. A theoretical model that calculates the interparticle force or tensile force between two adjacent particles was proposed based on the force balance equations. The theoretical model elucidates the phenomena in a laboratory experiment well and provides an insight into the formation mechanism of vertical joints in a uniform soil. The results highlight the generation of vertical joints in the initial deposition stage of loess with a uniform particle arrangement. Besides, the tensile force that contributes to the joint formation arises from the matric suction and surface tension of the solid-water-air contractile film.

The Effects of Long‐term Fertiliser Applications on Soil Organic Carbon and Hydraulic Properties of a Loess Soil in China

AbstractBased on a 28‐year in situ experiment, this paper investigated the impacts of organic and inorganic fertiliser applications on soil organic carbon (SOC) content and soil hydraulic properties of the silt loam (Eumorthic Anthrosols) soils derived from loess soil in the Guanzhong Plain of China. There were two crop (winter wheat and summer maize) rotations with conventional tillage. The treatments included control without fertiliser application, organic manure application (M), chemical fertiliser application (NP), and the application of organic manure with chemical fertiliser (MNP). The results showed that the 28‐year organic manure applications (M and MNP) significantly (p < 0·05) increased SOC content at surface layer (0–10 cm), but the effect of chemical fertilisers alone on SOC was not significant. Organic manure treatments (M and MNP) apparently improved soil hydraulic properties. Compared with control, field capacity and total porosity significantly (p < 0·05) increased while soil bulk density significantly (p < 0·05) decreased for organic manure applications. The M and MNP treatments increased soil water retentions by 3·2–10·8%, which was dependent of suction tensions. However, the NP treatment had no significantly impact on soil water retention compared with control. Neither organic nor inorganic fertiliser applications significantly changed saturated hydraulic conductivity. However, a clear difference was observed for unsaturated hydraulic conductivity between the M and the control at 0–5 cm. Overall, long‐term applications of organic manuring increased SOC content and amended soil hydraulic properties. However, the effects of chemical fertilisers on these soil properties were limited. Copyright © 2015 John Wiley & Sons, Ltd.

Nursery location and potassium enrichment in Aleppo pine stock 2. Performance under real and hydrogel-mediated drought conditions

Summary This work investigates Aleppo pine performance under severe drought conditions according to seedling size and nutritional status, with special emphasis on potassium. The interaction of drought ameliorating measures such as hydrogels is also studied. Seven fertilization treatments applied in two nursery locations provided 14 stocklots, resulting in different seedling sizes for each nutrient concentration and vice versa. Stocklots were tested in a greenhouse experiment and a harsh site plantation experiment. In the greenhouse, seedlings given two hydrogel doses (0.01 and 0.1 per cent w/w) plus a control were allowed to dry and survival and soil moisture were measured. In parallel to this trial, the effects of hydrogel dosage, brand and soil texture on soil water properties were tested in a laboratory. Results show that large stock survived signifi cantly better than conventionally sized stock in both experiments: 37 and 27 per cent more in the greenhouse and harsh site, respectively. Despite presenting wide variation, macronutrient concentration was not related to survival for a given size. Hydrogel effect on soil water was different according to factors, although in all cases , its effect diminished at suction tensions higher than 30 kPa. Results demonstrate the overriding effect of size over nutritional status on seedling survival in harsh environments.

Alterations in colonic barrier function caused by a low sodium diet or ionizing radiation.

This article reviews how cytokines and radiation-induced apoptosis affect the barrier function of the colonic pericryptal sheath and thereby colonic crypt fluid absorption. A layer of myofibroblasts forming a pericryptal sheath surrounds the colonic crypt epithelial cells. The colonic pericryptal hypertonicity (250--350 mM NaCl) resulting from Na(+) pumping into the space between the crypt epithelial cells and the myofibroblasts provides the driving force required to produce the suction tension (5-10 atmospheres) that dehydrates feces. [Na(+)] in the pericryptal space and crypt lumen is monitored in vivo with a Na(+) ion-sensitive fluorescent dye, Sodium Red. Dietary Na+ restriction increases this hypertonicity. The rate of dextran--labeled with fluorescein isothiocyanate (FITC--accumulation in the crypt lumen monitors fluid absorption by the crypt lumen. The rate of leakage of FITC dextran (10 kDa) across the crypt wall reflects its permeability. With low Na(+) intake, there is decreased crypt luminal dextran permeability. This decrease in crypt permeability is due to increased systemic and local release of angiotensin II and TGF-beta and is accompanied by pericryptal growth stimulation with consequent increased expression of myofibroblast proteins, smooth muscle actin, collagen 4, and OB cadherin. Inhibition of cytokine formation by the angiotensin-converting enzyme inhibitor (ACEI) captopril prevents these trophic effects. Colonic fluid absorption is inhibited 4 days after whole-body exposure to ionizing radiation of >8 Gy. Concurrently, there is loss of the pericryptal myofibroblasts resulting from apoptosis, with consequent loss of the barrier function of the pericryptal sheath. These effects cause increased rates of dextran leakage across the crypt wall and loss of myofibroblast markers. Normal colonic function returns after 10 days accompanied by repair of the pericryptal sheath. The caspase inhibitor, Z-VAD Fmk, reduces sheath apoptosis. Longer term irradiation of >8 Gy produces overgrowth of the myofibroblasts and fibrosis, which is inhibited by captopril.

Regional differences in rat large intestinal crypt function in relation to dehydrating capacity in vivo.

1. Rat descending colon absorbed fluid against a large hydraulic resistance, imposed by 10 % agarose (w/v) gel plugs inserted in the lumen, by raising the tonicity of the absorbate from the gel to 880 +/- 54 mosmol kg-1; the tonicity of the absorbate from 2.5 % gels was 352 +/- 38 mosmol kg-1. The hypertonic absorbate generated an osmotic pressure which created a fluid tension in the crypt lumen. This was monitored as a suction tension in colonic luminal gels of 45.3 +/- 3 cmH2O with 2.5 % gels and 725 +/- 145 cmH2O with 10 % gels. The caecum was unable to absorb fluid against a significant hydraulic resistance. 2. Fluorescein isothiocyanate-labelled dextran (FITC dextran; molecular mass 10000 Da) accumulated within descending colonic crypt lumens by concentration polarization. Maximal accumulation at a depth of 20-40 micrometer below the mucosal surface was 5.68 +/- 0.2-fold above control levels. Caecal crypts accumulated dextran to a maximum of 1.8 +/- 0.17-fold above control levels. 3. The relationship between crypt luminal tension and suction tension of the distal colon was also demonstrated using paraffin, which occluded the crypt lumens with microscopic droplets and completely inhibited fluid absorption from high resistance luminal gels. 4. Reduction in dietary Na+ intake raised plasma aldosterone and the capacity of the distal colon to dehydrate against a high luminal hydraulic resistance. The caecum did not respond in this way to varied Na+ intake.

DESEMPENHO DE UM INJETOR DE FERTILIZANTES DO TIPO VENTURI PARA FINS DE FERTIRRIGAÇÃO

Com o objetivo de avaliar as características hidráulicas de um injetor de fertilizantes do tipo Venturi, construído de polietileno, realizou-se um teste de desempenho em laboratório. O injetor utilizado foi o modelo Mazzei 1078, possuindo 200 mm de comprimento, 19,6 mm de diâmetro interno nas seções de entrada e saída e 7,6 mm de diâmetro interno no corpo cilindrico ("garganta"). Os testes foram realizados às pressões de alimentação de 10, 15, 20, 25 e 30 m.c.a., com os respectivos diferenciais de pressão: 2, 3 e 4; 4, 5 e 6; 4, 5 e 6; 6 e 7; 7 e 8 m.c.a.. Os parâmetros de desempenho analisados foram curvas de vazão de sucção versus tensão de sucção e rendimento. Os pares de valores de vazão de sucção e tensão de sucção foram submetidos à análise estatística de regressão, sendo o modelo linear o que melhor se ajustou aos valores observados. Para uma pressão de alimentação constante, a vazão de sucção aumentou com o aumento do diferencial de pressão e, para um diferencial de pressão constante, a vazão de sucção diminuiu com o acréscimo da pressão de alimentação. Para avaliar o rendimento do injetor foi desenvolvida, a partir das expressões que definem as energias piezométrica e cinética, uma equação utilizando os conceitos de potência motriz e potência útil. Para todos os diferenciais de pressão e pressão de alimentação estudados, o rendimento diminuiu com o aumento na tensão de sucção. O maior rendimento (16,28%) foi verificado para pressão de alimentação de 10 m.c.a., diferencial de pressão de 2 m.c.a. e tensão de sucção de 1,43 m.c.a. e o menor (1,87%) ocorreu para pressão de alimentação de 20 m.c.a., diferencial de pressão de 4 m.c.a. e tensão de sucção de 1,91 m.c.a..

Soil physical route survey and cable thermal design procedure

A thermal rating procedure is proposed for cables buried in sandy soils. The procedure uses a recently developed model to account for the effects of drying-out. The model requires as soil characteristics density, suction tension curve and saturated hydraulic conductivity. As boundary conditions it requires the ambient temperature and moisture content at cable level. In a reconnaissance survey of the cable route the thermally limiting soil sections are identified on the basis of estimated soil properties and local hydrology. Soil characteristics are determined in the laboratory for these sections only. The worst-case moisture content is derived from the lowest water table expected as indicated by hydromorphic characteristics of the soil profile. If evaporation and infiltration of precipitation influence the moisture content at cable level, a water balance model is used to calculate this value on the basis of climatological data. The accuracy of the procedure was investigated in a nine-year field experiment. It appears that, on average, the model predicts drying-out to occur more often than measured. In the case investigated the error may be expressed as, at the most, 0.1 in the pF-value (common logarithm of the suction tension) of the thermally undisturbed soil at cable level.

Improved method to calculate the critical conditions for drying out sandy soils around power cables

A numerical model has been developed, with which it is possible to calculate the critical thermal conditions at which drying out in sandy soils starts. This model is based on the theory of Philip and de Vries. Comparison of results of calculations with those obtained from extensive experiments on different types of sand shows that there is a reasonable measure of agreement. In particular, this is the result of taking into account both the effect of hysteresis in the relation between water content and suction tension and the effect of temperature upon this relation. It is indicated how the knowledge about these drying-out phenomena can be incorporated in the procedure of determining cable dimensions in practical cases. This knowledge enables quantification of the risk due to thermal runaway, which leads to a more efficient use of buried cables

Optimization of the water application in greenhouse tomatoes by introducing a tensiometer-controlled drip-irrigation system

This article deals with the results of a water-application experiment on greenhouse tomatoes ( Lycopersicum esculentum Mill.) in a temperate climate. The irrigation experiment conducted during 4 successive growing-seasons comprised, in addition to handling according to classical water application (i.e. non-controlled standard watering), 2 treatments in which the water was applied by means of a tensiometer-controlled drip-irrigation system. Both treatments with the drip-irrigation system differ from each other in the critical suction tension maintained in the root zone at a depth of 15 cm, a pF of 1.9 (the “wet”) and a pF of 2.2 (the “dry”) treatments, respectively. The water-application pattern exhibited a definite connection with the corresponding time course of the evapo-transpiration in the wet tensiometer-controlled treatment as opposed to that in the classical. The total irrigation volume in the dry tensiometer-controlled treatment was seriously reduced as compared to the wet. The moisture tensions in the plow layer continued to fluctuate within certain margins in both tensiometer-controlled drip treatments, without outstanding peaks. During the time which elapsed, some differences between the spring and autumn crops were noticed, particularly in the dry treatment. With respect to yield, there was no mutual difference between the tensiometer-controlled treatments, neither qualitatively nor quantitatively. This consequence arises primarily because the water deficit in the dry moisture level can be compensated for by capillary ascent from the phreatic surface. With the exception of the autumn crop of 1980, the yield in the tensiometer-controlled treatments was consistently better than in the control. The difference was not always equally significant in the matter of total yield, but it was certainly significant with regard to gradation and primarily with regard to average fruit weight.

Saugspannungsdiagramm für austrocknende Blätter von Quercus ilex L.

Summary Suction tension (depression of water potential) and osmotic pressure of young and mature sclerophyllous leaves of Quercus ilex were determined during desiccation until drought injuries occurred. The suction tension was measured with the Wescor Sample Chamber Psychrometer, the osmotic pressure by cryoscopy; from measured values of the osmotic pressure and the suction tension the turgor pressure was calculated. In leaves of Quercus ilex the suction tension does not fall to zero when the twigs are saturated with water, but remains at a level of about 4 bar (young leaves) to 9 bar (mature leaves). At water saturation deficits between the point of turgor loss and the appearance of the first drought injuries, the suction tension rises above the level of the osmotic pressure, thus indicating the effectiveness of negative turgor pressure. The higher the drought resistance of the leaves, the higher the values of negative turgor pressure and suction tension achieved.

DIFFERENCES IN GROWTH RATE AND SALT TOLERANCE BETWEEN VARIETIES OF THE HALOPHYTE CENTAURIUM LITTORALE (TURNER) GILMOUR, AND THEIR ECOLOGICAL SIGNIFICANCE

Four varieties of Centaurium littorale were cultured on Hoagland's nutrient solution with and without extra NaCl. The varieties investigated were var. littorale, var. iberoides (two biotypes), and var. latifolium from The Netherlands, and var. minus from England. The experimental plants were vegetative rosettes. The increase in fresh weight, the shoot:root ratio, the dry matter content, and the mineral composition of the leaves were determined. There appear to be infraspecific differences in growth rate. These agree with maximal plant size in the field. The growth rate in C. littorale is determined by the shoot:root ratio, the dry matter content of the leaves, but also by the leaf morphology. The physiological properties of the varieties investigated were affected in the salt treatments. Growth was reduced by a suction tension of 3.51 atm NaCl. The disturbance of the ionic balance by the accumulation of NaCl is a major factor in this growth reduction. Var. latifolium seems to have a low salt tolerance, which is in agreement with its occurrence on almost desalinized salt marshes.

Erhöhte Saugspannungswerte und morphologische Veränderungen durch transversale Einschnitte in einem Taxus-Stamm

Summary Total suction tension (or, according to the ψ -nomenclature, total water potential) at a certain point in the plant body is the sum of three components: S = S H + S B + S R , with S H =hydrostatic tension, S B = static soil tension and S R = frictional tension due to water movement in soil and plant. Experimental increase of the total tension is usually achieved by reducing the soil water content. This approach has a readily measurable effect on S B , but it must also influence the soil component of S R to an extent not easily assessed. Since both S B and the soil component of S R act from outside the plant body, variations in the irrigation pattern do not provide a means to influence selectively the tensions in a certain region of the plant body while leaving other parts unchanged. In a large tree, however, total tensions at various heights above ground are widely different. This is due far more to an increase with height I of conduit resistances (i. e., S R ) than to the simple height effect of S H . The influence of S R on tota potentials in the crown of a large tree may be simulated experimentally by means of a double sawcut in the stem of a small tree, which increases transport resistances of the conduit. In the early spring of 1972, such an experiment was set up with a large bush of yew ( Taxus baccata , L.), and suction tensions were followed with a pressure bomb. Diurnal courses of suction tensions are presented for typical days. Some general trends become evident: 1. Tensions are always higher in the experimental part than in the control, but the extent of the difference depends on the climatic conditions. 2. Values in the control reach a minimum in the late evening, while those in the experimental twigs continue to decline during the night. An eventual coincidence of the two curves is prevented by the onset of transpiration in the morning. 3. Tensions in the control follow changes in the vapour pressure deficit rather closely, while the experimental part shows a tendency to hold a plateau value at about 21 atm under different atmospheric conditions. Thus, maximum tension differences occur whenever there is a sudden fall in Δ p-values. Such a situation leads to a rapid tension drop in the control twigs, while the experimental parts remain at their previous high level, sometimes for a prolonged period. It is supposed that differences in the tension pattern similar to those described may play an important role in the establishment of physiological and morphological differences between lower and upper crown of a high tree. Shoot and needle lengths and needle distances were compared for experimental and control parts in 1972 and 1973. Results agree with previous work on artificial drought and its morphological consequences in conifers. Since in most earlier experiments drought was induced in young plants by means of infrequent irrigation, the similarity of results obtained in an old tree by the sawcut technique seems to be of some significance.

Saugspannungsmessungen in der Krone eines Mammutbaumes (Sequoiadendron giganteum)

Summary Scholander’s pressure chamber technique was used for determining suction tensions (= xylem water potentials) in the crown of a giant sequoia, Sequoiadendron giganteum (Lindl.) Buchholz. The influence of repeated cutting on readings was found to be considerable, when 20 minutes had elapsed between detachment of a branch and removal of a piece of stem. Equilibrium pressures became smaller in lateral shoots removed after some time from cut branches, indicating a withdrawal of the water column from the first cutting, probably through water uptake by leaf cells. Excessive trimming of branches and gradual detachment of small twigs from cut branches are not recommended, therefore, unless immediately after the first cutting. Daily fluctuations of suction tension at 7 m above the ground show a good agreement between vapour pressure deficits calculated from meteorological data and tensions in shaded twigs. Xylem tensions in twigs exposed to full sunlight gradually rise over the shadow curve from morning to noon, reaching a maximum difference of ∼ 7 atm. Minimum tensions are observed shortly before sunrise. Tension gradients from the lowest branches (7 m above ground) to the top (24–28 m) show only a slow rise when transpiration is reduced, especially immediately before sunrise. During the day, they are steeper in the shade (e.g. under cloudy sky) than in full sunshine. Measurements of potential osmotic pressures indicate that twigs in the top of the crown are unable to heighten their tensions as much as lower twigs because of osmotic difficulties. These are overcome in winter and early spring, when potential osmotic pressures are high and permit very steep gradients in full sun. A formula originally developed by Huber is further improved and serves as the basis for a discussion of static and dynamic components of xylem tensions.

GROWTH-PHYSIOLOGY, SALT-TOLERANCE AND MINERAL NUTRITION OF CENTAURIUM LITTORALE (TURNER) GILMOUR: ADAPTATIONS TO ITS OLYGOTHROPHIC AND BRACKISH HABITAT

Centaurium littorale was cultured under various conditions of nutrient availability, salinity and pH. The mineral composition of the experimental plants and of plants from a field site was investigated. The highest relative growth rate observed was 0.02 mg.mg.−1 day−1 and the shoot: root ratio was 0.8. Optimal growth occurred at very low nutrient availability. Suction tensions below 7 atm had no strong effect on the growth rate. There was a marked accumulation of NaCl in the tissues without a negative effect on the uptake of nutrient ions. In the pH-range 7.7–4.8 growth was equal. In its growth physiology and mineral nutrition Centaurium littorale is well adapted to the habitat: the brackish and poor young dune soil.

Interpretation of ectodesmata in relation to susceptibility to plant viruses

Ectodesmata were demonstrated in the outer walls of epidermal cells of French bean following treatment of leaf tissue with Gilson's solution.There was little change in the number of demonstrable ectodesmata with increasing age of the plant or as a result of increased suction tension of the culture solution. The number of ectodesmata was greater after darkening for 24 h but was not increased further with an additional period of darkening.These results are discussed in relation to studies on susceptibility to plant viruses and the structural evidence for ectodesmata. It is suggested that ectodesmata do not determine susceptibility to plant viruses and are not equivalent to the infectible site.

THE EFFECT OF LEAF WATER BALANCE ON THE SUSCEPTIBILITY OF FRENCH BEAN TO TOBACCO NECROSIS VIRUS

French beans were germinated under constant temperature, relative humidity, and day period, and were transferred to Hoagland's culture solution. Variations of the preinoculation treatment were begun at an age of 10 days for a period of 24 h. Treatments were selected which would induce turgor changes in the primary leaves.It was observed that susceptibility to tobacco necrosis virus infection was increased by preinoculation conditions of continuous darkness, high relative humidity, and low suction tension of the culture solution. Susceptibility was lowered by preinoculation conditions of continuous light, low relative humidity, and high suction tension of the culture solution.Diffusion pressure deficit, osmotic pressure, and turgor pressure measurements were made with the primary leaves at time of inoculation. Considerable agreement was noted between turgor changes and susceptibility.Preinoculation treatments such as darkening will alter susceptibility through changes in turgor pressure. It is suggested that there may be a direct effect of leaf turgor on the number of infectible sites.

THE INFLUENCE OF THE SUCTION TENSION OF THE NUTRIENT SOLUTIONS ON GROWTH, TRANSPIRATION AND DIFFUSION PRESSURE DEFICIT OF BEAN LEAVES (PHASEOLUS VULGARIS)

The rate of leaf growth of seedlings of Phaseolus vulgaris at different osmotic concentrations of the root environment has been measured. Even a small increase of the concentration gives a distinct reduction in growth. This reduction is the more important the higher transpiration is. The relationship between rate of growth, transpiration rate, osmotic value and diffusion pressure deficit has been determined. Application of the suction tension during 24 hours only has resulted in a fully reversible inhibition.

THE REGULATING INFLUENCE OF TRANSPIRATION AND SUCTION TENSION ON THE WATER AND SALT UPTAKE BY THE ROOTS OF INTACT VICIA FABA PLANTS

In the above a survey is given of the experiments on the water uptake described in preceding papers. It appeared that the water uptake is dependent on the suction tension in the xylem vessels and the water conductivity of the root tissue between medium and vessels. Important stress is laid upon the water conductivity of the tissue, this conductivity being not the same under various circumstances. It is shown that the water conductivity increases on enhancing the suction tension in the xylem vessels. As to the different root zones it appeared that in this case the conductivity of the tip zone did not alter, whereas the conductivity of the basal zones strongly increased. Moreover, such an increase in conductivity could be caused by enhancing the osmotic suction of the outer solution. Both the increased suction tension in the xylem vessels and the osmotic suction in the outer solution, cause a decreased turgescence of the root tissue. It is assumed that this decrease in turgescence is the direct cause of the enhanced water conductivity. Applying various inhibitors in different concentrations it could be stated that water uptake and water transport are completely passive processes. In spite of this the water transport is controlled by the living protoplasm, because of the fact that inhibitors in high concentrations reduced the water uptake. It is assumed that this is caused by changes in the structure of the protoplasm. Besides, the anion uptake of the various root zones is investigated. An apparatus to make possible these measurements is described. At low water uptake the maximum anion uptake is found in the apical root zones, the basal zones showing a rather small anion uptake in this case. Increasing the water uptake the anion uptake increases, this increase being most important in the basal zones. Moreover, on using respiration inhibitors in various concentrations it appeared to be possible to inhibit the anion uptake without reducing the water uptake. On the other hand an osmotic counter suction in the outer solution reduces water uptake without diminishing the anion uptake. Both processes water uptake and anion uptake, therefore, are related to one another, but this is not a direct relation. Comparing the water uptake and the anion uptake of the different root zones at low and high suction tension in the xylem vessels, it appears that the water uptake increases more than the anion uptake. The water conductivity of the different zones, however, increases to the same ratio as the anion uptake. An explanation of this phenomenon can be obtained via the respiration. The respiration of the different root zones and also the salt respiration is the same at low and high water uptake. Accepting the hypothesis that the respiration delivers the energy for the anion uptake there is reason to assume that the driving force of the salt uptake is the same at low and high water uptake values, therefore, also at low and high anion uptake values. As a consequence of this fact the anion uptake at high suction tension in the xylem vessels is as much facilitated as the water uptake, or in other words the conductivity for water and anions is increased to the same degree. It is assumed that this is a reasonable explanation as to the influence of the water uptake on the salt uptake. Moreover, such an influence can only be expected if the resistance to the salt transport is the limiting factor in the salt uptake process. A number of experiments are described dealing with the ratio between the total uptake and the amounts bound in the root tissue. The latter is more or less independent of the water uptake. Anatomical studies show that the whole root up to at least 20 cm from the root tip, has a non-suberized epidermis and an endodermis in its primary stage. The difference between the various root zones, therefore, must be ascribed to physiological features such as a difference in age.