Relationships between Root System Water Transport Properties and Plant Size in <i>Phaseolus</i>

Fiscus, Edwin L.; Markhart, Albert H.

doi:10.1104/pp.64.5.770

Cited by 86 publications

(39 citation statements)

References 6 publications

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“…Determination of these coefficients based on the freezing point depressions of the exudates yielded the same results so that the use of conductivity as a measure of the osmotic concentration appears to be justified in this instance. The coefficients presented thus far serve to demonstrate that the systems were behaving well and were comparable to those previously described (1,2).…”

supporting

confidence: 53%

“…= C"(l -a)J. + wAnl + J,* (2) J, is the volume flux density in cm' cm-2 s-', Lp the hydraulic conductance in cm3 cm-2 s' bar-', AP and AlI the hydrostatic and osmotic pressure differences across the root in bars, a the osmotic efficiency or reflection coefficient, J., the solute flux density in mole cm-2 s-', C the concentration in mole cm-3, the superscripts o and i refer to the outside and inside of the root respectively, w the coefficient of solute mobility in mole cm-2 S-' bar-', R the universal gas constant in cm3 bar mol-' K<', T the absolute temperature in K, and J. * the active solute transport rate in mole cm-2 s-'.…”

mentioning

confidence: 99%

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Abscisic Acid Transport Coefficients of Phaseolus Root Systems

Fiscus

Stermitz²,

Amoros³

1982

Plant Physiol.

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Diffusive and convective transport coefficients of Phaseolus vulgaris L. cv. Ouray root systems for abscisic acid for (ABA) were measured. The convective coefficient (reflection coefficient or osmotic efficiency factor) a was determined to be 0.% for ABA while the diffusive coefficient, c, was found to be 1.44 x 10-11 mole per square centimeter per second per bar.Steady-state concentrations of ABA in the root system exudates were not achieved until at least three hours after the applications suggesting either a slow saturation of binding sites or equilibration with tissues surrounding the xylem.Much of the methodology for determining the mode of action of ABA in the whole plant or in organs depends upon a supply of exogenous ABA. ABA has been applied to plants or plant parts in a wide variety of ways. One especially useful mode of application, which allows the plant to remain intact, is adding the ABA to the root medium of hydroponically grown plants. A L13 1002 area meter. The chamber was brought to the specified pressure and temperture (25 ± 0.25°C) and equilibrated overnight. In the morning, the system was checked for steady-state conditions, arbitrarily specified as changes in the volume and solute fluxes of less than ± 2% h-'. The total volume flux was measured at regular intervals and was expressed as the total volume flux per unit leaf area Qp,,3 as a means of comparing plants of different sizes (2). Unpublished data from this laboratory show that the ratio of projected leaf area to root surface area is constant and approximately 1 so that Qpl will approximate the volume and solute flux densities through the roots. The electrical conductivity of the exudates was measured and the concentration expressed as equivalents of KCI cm 3. The samples were immediately frozen for future ABA analysis and for osmotic pressure determinations by freezing point depression. Having established steady conditions according to the above criteria, the ABA (Sigma ± cis-trans), dissolved in 95% ethanol, was added to the system through an injection port without decreasing the pressure. The quantity of ABA added was calculated to yield the same approximate dose (1.5 x l0-7 mol cm-2 leaf area) in each case.ABA Analysis. Analyses of ABA in the exudates and nutrient solutions were conducted using HPLC. A [L-Porasil column was used in a Waters Associates system with a model 6000A pump operating at 3,000 p.s.i. The flow rate was 2.0 ml min-' and a UV detector was used operating at 254 nm. The eluting solvent was prepared by shaking a mixture of 350 ml acetonitrile and 700 ml chloroform with 300 ml 0.17 N acetic acid. The organic layer was separated and run through a micropore filter prior to use. With these conditions and solvent, the ± cis-trans ABA had a retention time of 4.0 minutes.One-ml samples of nutrient solution or exudate were brought to about pH 2 by the addition of 4 drops of 1 M HCI. The solutions were then extracted 3 times with 1.5 ml ethyl acetate. The ethyl acetate layer was evaporated to dryness in vacuo at ...

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supporting

confidence: 53%

mentioning

confidence: 99%

Abscisic Acid Transport Coefficients of Phaseolus Root Systems

Fiscus

Stermitz²,

Amoros³

1982

Plant Physiol.

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“…Following the development (Eqs. [2][3][4][5][6][7][8][9][10][11] in the same fashion as before leads to Fig. 9).…”

Section: )mentioning

confidence: 87%

An Interpretation of Some Whole Plant Water Transport Phenomena

Fiscus¹,

Klute²,

Kaufmann³

1983

Plant Physiol.

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A treatment of water flow into and through plants to the evaporating surface of the leaves is presented. The model is driven by evaporation from the cell wail matrix of the leaves. The adsorptive and pressure components of the ceDl wail matric potential are analyzed and the continuity between the pressure component and the lquid tension in the xylem estabUshed.Continuity of these potential components allows linking of a root transport function, driven by the tension in the xylem, to the leaf water potential. The root component of the overal model allows for the solvent-solute interactions characterstic of a membrane-bound system and discussion of the interactions of environmental variables such as root temperature and soil water potentials. A partition function is developed from data in the literature which describes how water absorbed by the plant might be divided between transpiration and leaf growth over a range of leaf water potentials.Relationships between the overall system conductance and the conductance coefficients of the various plant parts (roots, xylem, leaf matrix) are established and the influence of each of these discussed.The whole plant flow model coupled to the partition function is used to simulate several possible relationships between leaf water potential and transpiration rate. The effects of changing some of the partition function coefficients, as well as the root medium water potential on these simulations is illustrated.In addition to the general usefulness of the model and its ability to describe a wide range of situations, we conclude that the relationships used, dealing with bulk fluid flow, diffusion, and solute transport, are adequate to describe the system and that analogically based theoretical systems, such as the Ohm's law analogy, probably ought to be abandoned for this purpose.Frequently the question arises about what type of relationship one should expect between leaf water potential (4/), transpiration rate (7), and root medium water potential (4, for either soil or solution). The most frequently used model is related in some way to the Ohm's law analogy. The most frequently used interpretation of this analogy (correct or not) and therefore the answer to the question raised above is that we should expect a linear relationship between the soil-leaf potential difference and transpiration which passes through the origin. In this paper, we will reexamine this question on an elementary level and show several reasons why such expectations are not necessarily well founded. It is the purpose of this paper to present a model of whole plant water flow, to examine how this model might respond to changes in various parameters, and to settle on whether our expectations based on the Ohm's law analogy are reasonable.

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“…According to Fiscus and Markhart (1979), the system size seems to be the dominant and root permeability the minor factor. Also age of the root seems relatively unimportant for the nutrient uptake (Clarkson and Hanson 1980).…”

Section: Efficiency Of Root Systemmentioning

confidence: 99%

Effect of soil compactness on the growth and quality of carrot

Pietola¹

1995

AFSci

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Field experiments were performed in Southern Finland on three soil types: fine sand (1989-1991), clay (1989) and mull (1990-1991). The following soil mechanical treatments were applied to autumn ploughed land: soil loosening by ridge preparation (ridge distance 45 cm), rotary harrowing (to a depth of 20 cm, clay 15 cm), and soil compaction track by track by a tractor weighing 3 Mg (1 or 3 passes, wheel width 33 cm) before seed bed preparation. One plot was untreated. These treatments were set up in April (on clay in May) under moist soil conditions. Sprinkler irrigation (one application of 30 mm) was applied to clay and fine sand when soil moisture in top soil had decreased to around 50% of plant-available water capacity. PVC cylinders (r = 15 cm, h = 60 cm) were fixed in the experimental areas during the growing periods. At harvest, these cylinders were removed for specific analysis of tap and fibrous roots of carrot. Length and width of fibrous roots were quantified by image analysis in the USA. The impacts of soil loosening and partial compaction were determined by measuring soil physical parameters to a depth of 25 cm in mineral soils, and to greater depths in organic soil. Dry bulk densities of the plough layers increased with increasing tractor passes by 8%, 10% and 13% for fine sand, mull and clay soils, respectively. The lowest dry soil bulk density in the plough layer was obtained by rotary harrowing to a depth of 20 cm. Comparison of gamma ray transmission and gravimetric analysis indicated that dry soil bulk density was slightly lower when determined by gravimetric analysis. Increased soil bulk densities were reflected by increased water retention capacity (matric suction ≤ 10 kPa) and greater penetrometer resistance. Relatively similar increases in bulk density increased the penetrometer resistance much less in mull than in fine sand. In contrast, greater bulk densities in the mull soil affected soil air composition adversely by decreasing the O2 content to 10% when the subsoil had high wetness. In other soils, the lowest soil oxygen contents of 16-18% were recorded in early summer (compacted clay) and during periods of vigorous plant growth (fine sand) when soil water contents were high. Even though the highest degree of soil compactness (D) in a plough layer approached 93 (gravimetric) in all soils, only clay soil was compacted to a soil macro-porosity below 10% (pore diameter > 30 μm). Soil compaction promoted crop establishment and early growth as compared with loose soil beds. Optimum soil compactness for carrot yield (D = 82) was observed only in clay field where excess loosening or compaction affected yield quantity adversely at different stages of growth. During biomass accumulation, excessive penetrometer resistances limited tap root growth in compacted fine sand without irrigation. Water applications promoted shoot growth, but did not affect final shoot and tap root yield. Among the three soil types tested in this study, compaction of mull soil had the least effect on carrot growth and external quality. This paper presents evidence that the internal quality of carrots is only slightly affected by changes in soil physical properties, while the adverse effects of soil compaction on carrot external quality (short, deformed and conical tap roots with greater maximum diameters) are clear. Even though compacted clay soil greatly limited the biomass accumulations in the tap root, which had a high crude fibre content, the carotene (10 mg/100 g carrots) and sugar contents (5%) reached acceptable levels. The lowest carotene contents (4 mg/100 g carrots) were observed in loose mull, following a cool late summer in 1990. The effect of irrigation on carotene content varied from one year to another. High sugar and carotene contents appeared to respond to the high below-ground absorption surface. The fibrous root system of carrots, consisting of mostly very fine roots (diameter 0.15 mm), had total lengths of 150 m in loose fine sand at a soil depth of 0-50 cm (rotary harrowed), 200 m and 300 m in fine sand and mull soils subjected to 3 passes by a tractor wheel. The maximum dry weight (60 μg), length (1.2 cm) and surface area (0.05 cm2) of the fibrous root system per soil volume (cm3) were observed in compacted or irrigated soil to a depth of 30 cm, and also in relation to tap root dry weight. This suggests a capacity of carrot plant for high below-ground absorption potential and optimal biochemial maturation of tap root tissue even when surface soils are compacted. This is supported by higher leaf area, as the early shoot growth was promoted by partial soil compaction. Soil compaction affected the soil physical properties and carrot external quality in agreement with previous studies. Carotene and sugar contents appeared to be unaffected or were slightly increased in riper and firmer carrots of compacted soils. This is consistent with the earlier information about the internal quality of carrot which is shown to be highly dependent on genetic factors and developmental stage of carrot. The present study emphasizes the surface area of carrot fibrous root system as a beneficial factor for maintaining high levels of carotene and sugar contents in tap roots after partial soil compaction.

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Relationships between Root System Water Transport Properties and Plant Size in Phaseolus

Cited by 86 publications

References 6 publications

Abscisic Acid Transport Coefficients of Phaseolus Root Systems

Abscisic Acid Transport Coefficients of Phaseolus Root Systems

An Interpretation of Some Whole Plant Water Transport Phenomena

Effect of soil compactness on the growth and quality of carrot

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