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  • 1
    Electronic Resource
    Electronic Resource
    An analysis of resistance to water flow through wheat and tall fescue leaves during pressure chamber efflux experiments (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 8 (1985), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. This is a physical analysis of water movement in wheat (Triticum) and tall fescue (Festuca arundinacea) leaves placed in the Scholander pressure chamber. It takes into account the efflux resistances of water movement through the xylem and water flow across the cell membranes. Xylem resistance was estimated using Poiseuille's law.Leaves which had been pressurized in the chamber were embedded, sectioned, examined under a light microscope and photographed. Cells were intact but distorted and xylem vessels were intact. Cells in portions of the blade squeezed by the chamber sealing grommet were crushed, but xylem vessels remained intact.By applying pressure several tenths of a megapascal in excess of the balance pressure, water was forced from each leaf through the severed end which protruded from the chamber. Efflux curves were drawn by plotting the total water expressed as a function of time after the pressure increase. Water efflux from the shortest wheat leaf lasted only 10 min while efflux from the longest continued for up to 40 min. The efflux from a tall fescue leaf which was rehydrated and cut to a shorter length was much more rapid than efflux from the original leaf.Experiments combined with mathematical analysis suggested that the effect of leaf length on efflux is related to a high resistance to water flow through vascular bundles. Xylem resistance would be sufficient to produce this effect if it were 10 times greater than that predicted by Poiseuille's law. Both the observations of water flow from the cut end of the leaf and the mathematical model suggested very little water flows from bundles with vessels of diameter less than 12 μm. The apparent explanation is high resistance to water flow through these small diameter vessels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1985.tb01213.x
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  • 2
    Electronic Resource
    Electronic Resource
    FREEZE-ETCH ULTRASTRUCTURE OF WAXY MAIZE AND ACID HYDROLYZED WAXY MAIZE STARCH GRANULES (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 43 (1978), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Freeze-etching was used to study the ultrastructure of waxy maize starch and acid-treated (0.5M HCl, 25°C, 24 hr) waxy maize starch. The outer surfaces of the untreated granules were smooth with a faint fibrillar pattern. Granule cross-fractures had a fine particulate appearance with some radially-oriented ridges. Internal cracks were evident. Starch granules soaked in acid developed surface pits. Areas of hydrolysis had a distinctive structure and occurred in restricted zones. The shape of the acid-treated starch granules remained unchanged. However, inner regions showed extensive ultrastructural changes and water infiltration. Freeze-etching revealed bands of alternating high and low water content which formed lamellae in a few granules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1978.tb02403.x
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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