摘要:

Previous investigations of sporopollenin using13C Solid State Nuclear Magnetic Resonance have demonstrated differences between the major groups of plants in the composition of this acetolysisresistant biomacromolecule. The work presented here corroborates these results and suggests that sporopollenin obtained from seed megaspore-membranes differs slightly from that of pollen from the same plant group. Spectra obtained using NMR have been subjected to multivariate analysis. This approach has provided information which may be interpreted in phylogenetic terms. A number of fossil sporopollenins have also been investigated. These all show considerable degradation through diagenesis but retain certain characteristics of the original sporopollenin composition. Microspores and megaspores from the same species of Carboniferous arborescent lycopsid have also been investigated with a view to discerning any differences in composition that may exist between these sources of sporopollenin in the fossil record. Investigation of the effects of acetolysis on spore walls has also been undertaken. Together with the above work, this contributes to our understanding of the chemical composition of sporopollenins and the way in which this substance is affected by a treatment commonly used in the preparation of exines.

ISSN:0017-3134    

DOI:10.1080/00173139309427446

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Tracer experiments were carried out with anthers ofTulipacv. Apeldoorn andCucurbita maxima. Labelled sporopollenin fractions were enriched either by a conventional harsh or by a gentle method. In each case phenylalanine was incorporated at higher rates into the sporopollenin fraction ofTulipathan any of the other precursors used. The high incorporation of phenylalanine was observed at several stages of the postmeiotic development ofTulipaanthers. Even higher incorporation rates were obtained usingCucurbitaanthers. The incorporation of [U-l4C]-phenylalanine, [ring U-14C]-phenylalanine and [l-14C]-phenylaIanine into the sporopollenin ofTulipawas compared. The results indicate, that the whole carbon skeleton of phenylalanine is incorporated, pointing to an involvement of the phenylpropanoid metabolism. After potash fusion of a sporopollenin fraction labelled via [ring U-14C]-phenylalanine, p-hydroxybenzoic acid was the main labelled product among the ether soluble acids.

ISSN:0017-3134    

DOI:10.1080/00173139309427447

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The resistant remains of salvinialean microspore massulae and megaspores have been analyzed using scanning and transmission electron microscopy and Curie-point pyrolysis. The results show a selective enrichment of specific tissues in the fossil samples. The resistant compound, sporopollenin, in these fossil remains, is shown to consist of an oxygenated aromatic, and an aliphatic moiety. The latter is selectively enriched during diagenesis and upon oxidation. The organic matter of the extant samples is dominated by compounds which, during diagenesis, are selectively removed. The morphologically distinct megaspores and microspores are chemically comparable. Furthermore, although the genera studied are strongly distinctive in morphology and ultrastructure, the variation in their chemistry is too small to use for chemotaxonomy.

ISSN:0017-3134    

DOI:10.1080/00173139309427448

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Certain megaspores from the genusSelaginella(Lycophyta) and similar fossil genera of Cretaceous and Tertiary age are known to demonstrate a remarkable, iridescent appearance. Recent work on the spore wall ultrastructure shows that this iridescence is produced by a complex, ordered, particulate organization which is analogous to that of iridescent virus aggregates, precious opal and other synthetic materials. Our results suggest that this effect is produced by the accumulation of the spore wall material in the form of a monodisperse colloidal crystal. Colloidal organizations can also account for adjacent non-iridescent wall layers, the transition zones between these and the colloidal crystal and for spore walls with no hint of regular organization. The brief time in which the distinctive ordered exine ultrastructure develops and its occurrence around non-viable spore protoplasts add weight to the hypothesis that the exine is largely self-assembling. This new model of spore wall formation may well have wider implications in terms of current concepts of exine organization and development.

ISSN:0017-3134    

DOI:10.1080/00173139309427449

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This paper presents, for the first time, new information obtained from a research programme on the biopolymer organization of the sporoderm. The results are as follows: 1. In the TEM photographs of the partially degraded exine ofPinus griffithiiMcClell., 3.0 Å diameter molecular units were observed with fivefold symmetry. Using the modified Markham rotation method, secondary points of symmetry were also observed indicating that the quasi-crystalloid organization is at the molecular level. 2. In the partially degraded and fragmented wall ofBotryococcus brauniiKütz., obtained from fossil colonies extracted from the Hungarian Oil Shale, two kinds of biopolymer structures were observed in the same fragment. One type was a quasi-equivalent globular unit with a diameter of 50–75 Å, whereas the other type consisted of peculiar quasi-crystalloid pentagonal polygons with a diameter of 20–30 Å. Symmetry operations involving the points of the biopolymer structured wall of the fossilBotryococcusalgae were made for the first time. A quasi-crystalloid skeleton was also demonstrated as present in this cell wall. 3. A three dimensional model of the sporoderm quasi-crystalloid skeleton was established. A complete model of the Penrose-II type biopolymer structure is presented here. This model contains one central unit, surrounded by two types of Penrose-I units. Eight units can be directly attached to the central unit. An additional six units may be attached to the previous ones by asymmetrical connections. The „large frustrations”,sensuNelson 1986, are also asymmetrical with a peculiar asymmetry which can be observed in this large biopolymer model.

ISSN:0017-3134    

DOI:10.1080/00173139309427450

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue

ISSN:0017-3134    

DOI:10.1080/00173139309427445

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor