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A model for the pattern of deposition of microfibrils in the cell wall of Glaucocystis (1978)

Willison, J. H. M. ; Brown, R. Malcolm

Springer

Planta 141 (1978), S. 51-58

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ISSN: 1432-2048

Keywords: Cell wall ; Cellulose ; Freeze-etching ; Glaucocystis ; Microfibrils (cellulose) ; Morphogenesis ; Plasma membrane

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Freeze-fracturing of Glaucocystis nostochinearum Itzigsohn cells during cell-wall microfibril deposition indicates that unidirectionally polarized microfibril ends are localized in a “zone of synthesis” covering about 30% of the sarface area of the plasma membrane. Within this zone there are about 6 microfibril ends/μm2 cell surface. It is proposed that microfibrils are generated by the passage of their tips over the cell surface and that the pattern of microfibril organization at the poles of the cells, in which microfibrils of alternate layers are interconnected at 3 “rotation centres”, results directly from the pattern of this translation of microfibril tips. In a model of the deposition pattern it is proposed that the zone of synthesis may split into 3 sub-zones as the poles are approached, each sub-zone being responsible for the generation of one rotation centre. It is demonstrated that the microfibrillar component of the entire wall could be generated by the steady translation of the microfibril tips (at which synthesis is presumed to occur) over the cell surface at a rate of 0.25–0.5 μm min-1. Microcinematography indicates that the protoplast rotates during cell-wall deposition, and it is proposed that this rotation may play a role in the generation of the microfibril deposition pattern.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00387744

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The temperature dependence of the Raman spectrum of ammonium perrhenate (1978)

Korppi-Tommola, J. ; Devarajan, V. ; Brown, R. J. C. ; [et al.]

Chichester [u.a.] : Wiley-Blackwell

Journal of Raman Spectroscopy 7 (1978), S. 96-100

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ISSN: 0377-0486

Keywords: Chemistry ; Analytical Chemistry and Spectroscopy

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: Raman spectra of NH4ReO4 and ND4ReO4 have been recorded at several temperatures between 77 K and 353 K. As the temperature is increased, several bands due to both internal and external modes of the perrhenate ion are shifted to lower wavenumbers and there is a discontinuity in the slope of the wavenumber versus temperature curves near 200 K. This behaviour is correlated with recent NQR and X-ray diffraction results and supports the suggestion of a higher order phase transition near 200 K. The bands due to the ammonium ion vibrations are broadened as the temperature is increased and the librational lattice mode is no longer observable above about 200 K. The nature of the motion of the ammonium ion in the lattice is discussed and it is pointed out that the presence of a librational lattice mode does not necessarily indicate an absence of reorientational motion.

Additional Material: 5 Ill.