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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 8 (1985), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Large molecular weight solutes that do not penetrate the root have been used to correct for the surface film in measurements with mannitol of the volume of the Apparent Free Space (FS) in bailey roots. The results are compared with those obtained using other correction techniques for elimination of the surface film. Large molecules seem to be adsorbed on the root surface and the kinetics of adsorption differ between the polyhydric alcohol mannitol or the polysaccharide dextran on the one hand, and the polyether polyethylene glycol (PEG-4000) on the other. The significance of this difference in kinetics is discussed in relation to the use of PEG as an osmoticum in studies on root water relations and its effect on ion uptake. Although smaller molecular weight PEG's penetrate the FS and diminish sodium uptake from 10 mol m−3 NaCl, more dilute solutions of mannitol and larger PEG polymers are unlikely to affect ion uptake from dilute nutrient solutions. Use of these substances along with labelled nutrients in kinetic studies of the compartmentation of ions in roots can help to distinguish between ions associated with the surface film, those in the FS and those that have crossed the cell membranes into the protoplast.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 16 (1976), S. 0 
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Some of the factors affecting absorption and translocation of pesticides by the hypocotyls of intact radish (Raphanus sativus, L., cv. Black Spanish) seedlings have been studied, particular attention being given to the triazine herbicides simazine, atrazine and atraton. Uptake and translocation appear to be largely passive processes and by contrast with foliar absorption seem to be unaffected by humidity, con-centration, light and by the aqueous solubilities of the compounds. Diffusion across the tissues of the hypocotyl, rather than rate of transpiration, appears to determine the rate at which atrazine and simazine are translocated to the cotyledons. For several pesticides there is a qualitative relationship between the percentages of the compounds translocated to the upper portion of the shoots and their partition coefficients in oil/water systems. In conclusion, some consideration is given to the relative importance of uptake by roots and shoots under field conditions.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 12 (1972), S. 0 
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary. Evidence is presented that blackcurrants show a considerable tolerance to simazine when the entire root system is exposed to a uniform concentration of the herbicide in sand and water culture. The tolerance of this species under field conditions does not therefore seem to be primarily due to root development being limited in the surface soil to which simazine is applied. Accordingly, experiments were carried out using simazine, labelled in the ring with 14C, to determine whether there were restrictions to the uptake of the herbicide by the roots and its translocation to the xylem sap and leaves, and whether there was extensive breakdown of simazine in the plant. The results of these experiments are compared with those on two susceptible species, barley and marrow.Although simazine appeared to be metabolized to a greater extent in blackcurrants, and was less readily translocated from the roots, than in the susceptible species, a substantial proportion of the labelled material in the leaves was present as unchanged simazine. Studies on the effects of simazine on the rate of transpiration of detached leaves of the three species suggested that in blackcurrants there was a restriction to movement of the herbicide from the conducting tissue in the leaves to the mesophyll; this was confirmed by autoradiographs. It is suggested that this restriction, combined with partial breakdown of the herbicide in the leaves, may be responsible for the tolerance of blackcurrants to simazine.Résistance du cassissier à la simazine
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 194 (1962), S. 1235-1236 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] THE titration of gelatin with acids and alkalis A gives information on the net combining power of the basic and acidic groups on the protein molecules. This method has been used1'2 to estimate the position of the isoelectric point, at which the number of positively and negatively charged groups are ...
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 202 (1964), S. 314-315 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Solutions of silica were prepared by passing dilute aqueous sodium metasilicate through a cation exchange column packed with 'Zeokarb 225' in the hydrogen form. Detached roots of Hordeum vulgare, grown for 6 days in 10~4 M calcium sulphate solution, were allowed to absorb silica from solutions at ...
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Planta 86 (1969), S. 301-314 
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The absorption and subsequent distribution of sodium and potassium has been examined in maize seedlings in short-term experiments using sodium-22 and potassium-42. The absorption and translocation of sodium by different segments of intact seedlings was also investigated. Although absorption of potassium exceeded that of sodium by a factor of about 50, there was no evidence that the entry of sodium was confined to a small region of the root. Determinations of the relative quantities of sodium and potassium in the xylem exudate of detached roots showed that the ratio of sodium to potassium decreased with increasing length of the root. These results suggested that upward movement of sodium in the xylem vessels was progressively reduced towards the basal part of the root. This conclusion was supported by microautoradiographs, which showed that although the concentration of sodium within the endodermis was greater than that in the cortex, there was an apparent decrease in the sodium content of the major xylem vessels at the basal end of the root.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Roots of barley (Hordeum vulgare L.) plants which had been grown at 20° were cooled to temperatures of 12° C or lower for 1–5 days and then returned to 20° C when measurements were made of ion and water movement into the xylem after excision. Very marked increases in exudation were observed in cooled roots, sometimes as much as four times greater than in controls kept at 20° C throughout their life. There were no consistent increases in the concentration of K+, Ca2+ or H2PO4′ in the exudate from cooled roots and it was concluded that the extra water flow across the root occurred without any increase in the osmotic potential of the sap. Similar changes in ion absorption and translocation were found in intact plants transpiring either rapidly or slowly. Cooled roots contained appreciably more soluble carbohydrate than controls and when they were returned to 20° C their respiration was 50–120% greater. These changes were not, however, strictly correlated with differences in exudation in cooled and untreated roots. Cooled plants which had been heavily shaded respired at the same rate as controls but exuded sap at twice the rate. It is concluded that the effects of cooling on both exudation and the accumulation of roluble carbohydrate are consequences of reduced growth and the possible alteration of the selative amounts of growth substances in the root.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 53 (1980), S. 171-177 
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Measurements of the radial diffusion of tritiated water, combined with axial and radial flow in an artificial cylindrical membrane, are examined with the aid of a mathematical model. The results are used to assess how far measurement of diffusion of labeled water in plant roots may throw light on pathways of movement of water and on barriers to flow.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 111 (1988), S. 223-229 
    ISSN: 1573-5036
    Keywords: conductivity ; hydraulic ; hypodermis ; polarity ; roots ; water ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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