ISSN:0017-3134    

DOI:10.1080/00173139309429982

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The pollen morphology of the six SwedishCallitricheL. species was investigated using LM, SEM and TEM. The surface ornamentation is reticulate inC. stagnalis, C. platycarpa, C. cophocarpaandC. palustriswith supratectal elements in the first three species. The ectexine is reduced inC. hamulata, occurring as scattered granules, but completely absent inC. hermaphroditica. None of the species has distinct apertures butC. cophocarpaandC. platycarpaboth have leptomata. The ultrastructure of the pollen wall inC. palustrisshows regions with lamellated footlayer and an endexine which may function as apertures. Pollen morphology is found to be related to pollination biology; species with leptomata sometimes being pollinated through ephydrophily and species with reduced exine being hyphydrophilous.

ISSN:0017-3134    

DOI:10.1080/00173139309429983

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

After callose dissolution, the foot layer is formed on the surface of primordial lamella. Later the differentiation of endexine lamellae begins. The question of endexine and proximal aperture in primitive angiosperms is discussed. The first layer of intine contains lacunae and is built up with RER and Golgi, working in tandem. The second layer of intine is formed as the result of the activity of the special generation of dictyosomes. Special attention is paid to the tapetum which is of secretory type before the dissolution of callose and then is reorganized into a pseudoperiplasmodium type. Although orbicules are not formed, the tapetal cells are active. They form clusters of dark or light grey droplets, after callose dissolution which are visible in luminae of the mature sporoderm. Cytochemical treatment of these clusters with pronase and lipase was undertaken to ascertain their chemical nature. Sporoderm development with special reference to parallel changes in microspore organelles is depicted diagrammatically.

ISSN:0017-3134    

DOI:10.1080/00173139309429984

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Pollen of 108 species out of 18 genera (from all tribes of the Old World Gesneriaceae [subf. Cyrtandroideae]) was examined using light, scanning and transmission electron microscopy. The pollen grains are small sized, isopolar and 3-colpate or 3-colporate. In equatorial view they are mostly spheroidal (rarely suboblate or oblate), in polar view circular or subangular. The most variable character is the exine structure and -sculpture. The tectum is perforate, microreticulate, coarsely reticulate or rugulate. Further important characters of the tectum are (a) the presence or absence of conical supratectate sculptural elements, and (b) the width of lumina being either equal or exhibiting different at the apo- and mesocolpium. Ten exine types are distinguished. Some genera and species can be well referred to a special exine type, e.g.,Aeschynanthus, Epithema, Stauranthera grandiflora; in other genera several exine types occur, e.g., in the large and heterogeneous genusDidymocarpus. The pollen morphology of the two large subfamilies Cyrtandroideae and Gesnerioideae is compared.

ISSN:0017-3134    

DOI:10.1080/00173139309429985

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The pollen morphology and ultrastructure of 20 species ofCamellia(Theaceae) representing the four subgenera were examined. The pollen is tricolporate, spherical to slightly oblate or prolate, with scabrate to rugulate exine sculpturing. The tectum is traversed by perforations that vary in diameter. Pollen wall structure is tectate-columellate, the columellae fused to a footlayer. Endexine is present in all of the taxa examined. The greatest variation was observed in pollen size.

ISSN:0017-3134    

DOI:10.1080/00173139309429986

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Pollen grains of eieven species ofPariana, a small genus of herbaceous bamboos, were studied using LM, SEM and TEM. Ten of them have thePariana stenolemma-type of pollen characterized by areolate exine due to relatively high and well separated denticulate processes on a slightly undulated tectum, vestigial columellae and no distinct annulus. At the pore edge the foot layer is thickened and folded.

ISSN:0017-3134    

DOI:10.1080/00173139309429987

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Quantitative pollen-sculpture variation can provide systematically useful information. To test manual-outlining techniques used with automated measurement of pollen-sculpture features, we conducted several experiments in which perforations were traced with felt-tip pen onto thin sheets of plastic. In each experiment, seven individuals made five tracings of the same pattern. Tracings were then digitized and perforations measured using image-analysis software. Three test patterns were used: (1) an SEM micrograph with “real” pollen perforations; (2) a computer-generated test pattern that simulated very small pollen perforations; and (3) a computer-generated test pattern that simulated very large pollen perforations. Experiments examined the effect on precision and accuracy of using: (1) opaque-black versus transparent-red ink; (2) small versus large perforations; and (3) fuzzy- versus sharp-edged perforations. Tracings were statistically compared using the coefficient of variation and an analysis of variance. Tracings of computer-generated test patterns also were compared directly with the digitized test pattern. Results indicated that: (1) variation between tracings by a single individual will usually be very small; (2) variation between individuals usually will be statistically significant, even with the sharpest possible perforations; (3) tracing with opaque ink is more accurate than with transparent ink; (4) both precision and accuracy increase with perforation size; and (5) deviation of a single-tracing measurement from the parametric value usually will be much less than five percent. These experiments demonstrated that manual tracing of pollen perforations prior to image analysis can produce repeatable measurements accurate to two significant figures.

ISSN:0017-3134    

DOI:10.1080/00173139309429988

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Phosphate buffered saline (PBS) extracts of pollen of 34 out of 95 angiosperm species (in 40 families) tested, lysed human and/or snake head fish (Channa striatusBloch) erythrocytes during assay for lectins in pollen. The bitter taste of the pollen extracts of these 34 species, the formation of a stable foam on shaking and the ability to lyse erythrocytes, suggested the presence of saponins, which have not, so far, been reported from pollen. Thin Layer Chromatography (TLC) and Mass Spectrum (MS) of the erythrocyte-lysing extracts of pollen of the garden gladiolus (Gladiolus gandavensisVan Hout.) confirmed that the pollen contained both triterpenoidal and steroidal saponins. The implications for the presence of saponins in pollen inhaled from the atmosphere, in the diagnosis and management of pollen allergy are discussed.

ISSN:0017-3134    

DOI:10.1080/00173139309429989

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A continental stratigraphy column covering the Pliocene and Early Pleistocene in SE Shanxi, China has been studied using pollen analysis, ten pollen zones are defined with their correlation to magnetic polarity and10Be datings. The vegetational development and climatic changes during the period from 5.1 Ma to 1.8 Ma BP are discussed.Piceabecame a dominant component of the pollen assemblage in the Early Pliocene. Subtropical components such asCaryaandLiquidambaroccur in the Pliocene pollen spectra. The palaeoclimate of the Pliocene was moist and relatively warm, though a trend towards a colder and drier climate is reflected. Around 2.3 Ma BP the prevailing forest turned into a type of steppe and the subtropical components basically migrated out of the area. The Pliocene-Pleistocene boundary is also discussed using palynostratigraphy. It seems reasonable to place the Pliocene-Pleistocene boundary close to the Gauss-matuyama magnetic boundary.

ISSN:0017-3134    

DOI:10.1080/00173139309429990

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Microsporangiate structures,Brenneria potomacensisgen. et sp. nov., containing pollen grains similar to dispersedDecussosporitesare described from the Lower Cretaceous (Barremian or Early Aptian?) Potomac Group localities at Drewry's Bluff and Dutch Gap on the James River southeast of Richmond, Virginia. These fossils provide the first megafossil evidence of plants producingDecussosporites-type pollen and contribute important new information on the structure and possible systematic affinities of this unique Mesozoic gymnosperm. The microsporangiate structure is composed of an axis with helically arranged synangiate microsporangiate units, each unit consisting of two laterally fused sporangia borne on a short stalk. The pollen grains are very small, bisaccate, distinctly striate (taeniate) and TEM shows that they have partly infilled sacci (quasisaccate). These grains represent the youngest occurrence of saccate, striate pollen, which has not been recorded previously from sediments younger than the earliest Jurassic. Fossil seeds (Brennerispermum potomacensisgen. et sp. nov.) from the same localities asBrenneriacontainDecussosporitespollen in the micropyle, and are believed to have been produced by the same plant species. The seeds are small and unitegmic with a distinct megaspore membrane. The occurrence of seeds adhering together in groups indicates that they were borne in aggregations. The microsporangiate structures of Brenneria show some similarity to those of the ginkgophytes (Ginkgoales and Czekanowskiales), but there are substantial differences in the structure of seeds and pollen. TheDecussosporitespollen grains together with morphology of the reproductive organs support a closer relationship of theBrenneria-plant to previously described “Mesozoic pteridosperms”.

ISSN:0017-3134    

DOI:10.1080/00173139309429991

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor