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Living sieve cells of conifers as visualized by confocal, laser-scanning fluorescence microscopy (1992)

Schulz, A.

Springer

Protoplasma 166 (1992), S. 153-164

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ISSN: 1615-6102

Keywords: Conifers ; Endoplasmic reticulum ; Laser scanning microscopy ; Phloem transport ; Sieve areas

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary Confocal laser scanning microscopy (CLSM) and fluorochromes were used to visualize the assimilate-conducting sieve cells of conifers in vivo. When still nucleate, the cytoplasm of these cells shows streaming and occupies the cell periphery including the pitlike, thin wall regions where sieve areas would develop. During differentiation the nuclear fluorescence and the central vacuoles disappear. At maturity and after ER-specific staining the sieve areas are the most conspicuous character of sieve cells. Those linking two sieve cells are covered on either side with prominent amounts of ER, while those leading to a Strasburger (=albuminous) cell show fluorescence on the sieve-cell side only. Within the sieve-area wall fluorescence appears also in the common median cavity which is part of the symplastic path between sieve cells. Electron microscopy (EM) depicts the ER as complexes of densely convoluted tubules of smooth ER, equally on either side of a sieve area, provided that the fixation of this sensitive tissue is appropriate. Purposeful wounding causes a swelling and vesiculation of the ER-tubules which is visible in both CLSM and EM. Electron micrographs of ER-complexes at sieve areas -in this paper demonstrated in vivo -have often been argued to be artefacts, since they should raise flow resistance considerably and are not consistent with the Münch hypothesis on phloem transport. The implications of this location for phloem transport are discussed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01322778

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Fluorierung von Cyanurchlorid und Tieftemperatur-Kristallstruktur von [(ClCN)3F]+ [AsF6]- (1994)

Broschag, M. ; Klapötke, T. M. ; Schulz, A. ; [et al.]

Weinheim : Wiley-Blackwell

Zeitschrift für anorganische Chemie 620 (1994), S. 1132-1136

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ISSN: 0044-2313

Keywords: Cyanuric chloride ; FPDE values ; crystal structure ; chlorotrifluoro methane ; oxidative fluorinators ; ab initio computations ; Chemistry ; Inorganic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Description / Table of Contents: Fluorination of Cyanuric Chloride and Low-Temperature Crystal Structure of [(ClCN)3F]+[AsF6]-The low-temperature fluorination of cyanuric chloride, (ClCN)3, with F2/AsF5 in SO2F2 solution yielded the salt [(ClCN)3F]+ [AsF6]- (1) essentially in quantitative yield. Compound 1 was identified by a low-temperature single crystal X-ray structure determination: R 3c, trigonal, a = b = 10.4246(23) Å, c = 15.1850(24) Å, V = 1429.1(4) Å 3, Z = 6, RF = 0.056, Rw = 0.076 (for significant reflections), RF = 0.088, Rw = 0.079 (for all reflections). Fluorination of neat (ClCN)3 with [NF4]+ [Sb2F11]- yielded NF3, CClF3, SbF3, N2 and traces of CF4. A qualitative scale for the oxidizing strength of the oxidative fluorinators NF4+ and (XCN)3F+ (X = H, F, Cl) has been computed ab initio.

Notes: Durch Tieftemperaturfluorierung von Cyanurchlorid, (ClCN)3, mit F2/AsF5 in SO2F2-Lösung wurde [(ClCN)3F]+ [AsF6]- (1) in nahezu quantitativer Ausbeute dargestellt, aus SO2 bei Raumtemperatur umkristallisert und durch eine Tieftemperatur-Röntgenstrukturanalyse (-170°C) identifiziert: R 3c, trigonal, a = b = 10,4246(23) Å, c = 5,1850(24) Å, V = 1 429,1(4) Å3, Z = 6, RF = 0,056, Rw = 0,076 (für wesentliche Reflexionen), RF = 0,088, Rw = 0,079 (für alle Reflexe). Die Fluorierung von festem (ClCN)3 mit [NF4]+ [Sb2F11]- im Molverhältnis 1:2 lieferte NF3, CClF3, SbF3, N2 und Spuren an CF4. Eine qualitative Reihenfolge bezüglich der FPDE-Werte von NF4+ und (XCN)3F+ (X = H, F, Cl) wurde ab initio berechnet.

Additional Material: 3 Ill.