Determination of Hydraulic and Osmotic Properties of Soybean Root Systems

Fiscus, Edwin L.

doi:10.1104/pp.59.6.1013

Cited by 101 publications

(96 citation statements)

References 11 publications

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“…To allow more detailed comparisons between plants of different size or species or, as in the present case, between host and parasite, the whole-plant hydraulic conductivity L p is best related to the area of the semi-permeable membranes which exert impedance to water flow into the plant, namely the plasmalemma of root cortex cells (Fiscus, 1977) or the endodermal membranes (Passioura, 1984). As the area of neither of these was available, L p was related to the fresh weight of the roots, and in this way a specific conductivity (L p \root f. wt) was estimated.…”

Section: Hydraulic Properies Of Rhinanthus and Collection Of Xylem Samentioning

confidence: 99%

“…When attached to Trifolium, Rhinanthus showed a comparatively higher resistance to hydraulic flow (31i10* Pa s m −$ ) than with Hordeum as the host (Table 1). For more detailed comparisons between different plants, whole-plant conductivities L p need to be related to the area of the membranes which limit water flow, that is the plasmalemma of the root cortex cells (Fiscus, 1977) or the endodermal membranes (Passioura, 1984). As these were unavailable, the L p was related to root fresh weight, a parameter proportional to root membrane area, and the specific conductivity L p \root f. wt was calculated.…”

Section: Xylem Sap Collectionmentioning

confidence: 99%

See 1 more Smart Citation

Simultaneous collection of xylem sap from Rhinanthus minor and the hosts Hordeum and Trifolium: hydraulic properties, xylem sap composition and effects of attachment

Seel

Jeschke

1999

New Phytologist

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The facultative hemiparasite Rhinanthus minor was grown alone, or with either Hordeum vulgare or Trifolium alpestre as a host. All plants were fed 5 mM nitrate. In the parasites, successful attachment led to dramatic increases in growth (particularly with barley as host) and in tissue concentrations of total N, NO $ − , H # PO % − and K + , as well as moderate increases in Cl − and SO % #−. Mg# + and Ca# + concentrations either remained unchanged, increased or decreased, depending on the host. Xylem sap was collected from leaf veins (barley) or the stem (Rhinanthus and clover), by applying pneumatic pressure to the rooted soil to raise the soil water potential so that in vivo xylem sap exuded from small incisions once the applied pressure balanced the tension exerted by transpiration. High balancing pressures were needed for unattached Rhinanthus, whereas simultaneous collection of xylem sap from attached Rhinanthus and its host, at a much lower balancing pressure, was possible only when the parasite was enclosed in polyethylene film and high transpiration abolished. From plots of xylem sap volume flow versus applied pressure, the hydraulic conductivity L p and the overall hydraulic resistance r were obtained. The value of r was high in unattached Rhinanthus and dramatically decreased by attachment to a host, highlighting the improved access to water gained by Rhinanthus when parasitizing a host. For the parasites, attachment resulted in greatly increased concentrations and solute flow rates in xylem of K + , NO $ − , H # PO % − and amino acids, and decreased concentrations of Ca# + and Mg# + . Estimates of NO $ − reduction in the parasite showed that 99 % was reduced in unattached plants, 85 % in those attached to clover and 52 % in those attached to barley. In the parasitized hosts, ion concentrations in xylem sap were somewhat increased relative to unparasitized controls. Conversely, xylem sap amino-acid concentrations in infected hosts were decreased. Glutamine (Gln) was the principal amino acid in xylem sap of unattached Rhinanthus, but after attachment to both hosts asparagine (Asn) predominated. In clover, Asn was the major transport amino acid, suggesting massive transfer of Asn from host to parasite. In unparasitized barley, however, Gln was the major xylem sap amino acid, but unexpectedly, in this species Asn was induced as the principal amino acid when parasitized. The results are discussed in terms of mutual host-parasite interactions.

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Section: Hydraulic Properies Of Rhinanthus and Collection Of Xylem Samentioning

confidence: 99%

Section: Xylem Sap Collectionmentioning

confidence: 99%

Simultaneous collection of xylem sap from Rhinanthus minor and the hosts Hordeum and Trifolium: hydraulic properties, xylem sap composition and effects of attachment

Seel

Jeschke

1999

New Phytologist

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“…Transport coefficients for ABA, water, and solutes were determined by the procedures of Fiscus (1) based on the transport equations J, = LpAP -aRT(C" -C'), and (1) J. = C"(l -a)J.…”

mentioning

confidence: 99%

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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“…Fach root L^, measurement took approx. 7 h. The plot of volume flux versus applied pressure was nonlinear at low pressures and linear at higher pressures, as found by others (Lopushinsky, 1964;Fiscus, 1977). Root L,, was calculated as the slope of the cjrve relating volume flux to applied pressure, over the range of pressures where flow increased linearly with pressure (Fiscus, 1977).…”

Section: Methodsmentioning

confidence: 96%

“…Instantaneous L,, determinations are difficult to reproduce and may lead to erroneous conclusions regarding root L^,, especially when steady-state conditions are not employed (Fiscus, 1983). The current study was undertaken to examine differential root L^, in mycorrhizal and nonmycorrhizal green ash seedlings using the procedure recommended by Fiscus (1977). Preliminary experiments with green ash indicated that significant growth differences between inoculated and control seedlings could be eliminated with moderate levels of P fertilization, which had no apparent effect on root colonization (Andersen, Sucoff & Dixon, 1985).…”

mentioning

confidence: 99%

Root hydraulic conductivity of vesicular–arbuscular mycorrhizal green ash seedlings

Andersen¹,

Markhart²,

Dixon³

et al. 1988

New Phytologist

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SU M !M ARYGreen ash {Pra.xinus pennsvtvanica Marsh.) was either inoculated or not with Glomus etunicatum Becker and Gerd. and Rrown for 37 d to permit root colonization. Root hydraulic conductivity {L^) per unit length was measured on excised root systems to examine the influence of vesicular-arbuscular (VA) mycorrhiza inoculation, seedling size, phosphorus (P) nutrition, and biotnass distribution. Fertilization with P eliminated significant differences in seedling size and dry matter distribution between mycorrhizal (M) and non-mycorrhizal (NM) seedlings, but VA mycorrhizas increased root and leaf P concentration. Root L,, was similar in M and NM seedlings of similar size, and was lower in M seedlings for a given root P concentration. Root L^^ decreased with age and weight, and increased as the proportion of dry weight in the leaves increased in both M and NM seedlings. Mycorrhizal colonization had no significant effect on root /." in the absence of a significant growth response.

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Determination of Hydraulic and Osmotic Properties of Soybean Root Systems

Cited by 101 publications

References 11 publications

Simultaneous collection of xylem sap from Rhinanthus minor and the hosts Hordeum and Trifolium: hydraulic properties, xylem sap composition and effects of attachment

Simultaneous collection of xylem sap from Rhinanthus minor and the hosts Hordeum and Trifolium: hydraulic properties, xylem sap composition and effects of attachment

Abscisic Acid Transport Coefficients of Phaseolus Root Systems

Root hydraulic conductivity of vesicular–arbuscular mycorrhizal green ash seedlings

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