Pollen Surface Research Articles

Pollenmorphologie und Chromosomenzahlen der Poaceen-Subtribus Deschampsiinae Holub

Pollen morphology and ultrastructure of twenty-seven European species of the subtribe Deschampsiinae Holub were investigated by light, phase contrast and scanning electron microscopy. Genera are characterized by pollen size, development of the anuli and pollen surface. Comparison of the data with the known chromosome numbers and some karyotypes confirms the important influence of karyology on the size and fine structure of pollen.

Die Aufnahme bakterieller DNA in quellende und keimende Pollen von Petunia hybrida und Nicotiana glauca

Summary The uptake of bacterial DNA into swelling and germinating pollen grains of Petunia hybrida and Nicotiana glauca was investigated: 1. Autoradiography. A germination medium for pollen material from N. glauca was worked out (85 % germination). Pollen of N. glauca was incubated in this medium containing 14C-labelled DNA from Rhizobium leguminosarum (existing methods for the isolation of DNA from Rhizobium were improved), treated with DNase and used for autoradiography. The results (figs. 1–5) are consistent with a DNA uptake but can not prove it. 2. CsCl gradient centrifugation. a) A method for the isolation of native DNA from pollen grains was worked out. It includes DNase treatments for the removal of superficially bound DNA and treatments with Triton X-100 for the removal of DNase insensitive complexes eventually formed between the exogenous DNA and constituents of the pollen surfaces. Furthermore, Triton X-100 weakens the exine and thus enables the pollen to be released from the exine (figs. 5–7). b) Unripe pollen grains of P. hybrida were incubated with 3H-labelled DNA from a strain of E. coli carrying R-factors against kanamycin. By CsCl gradient centrifugation of the DNA isolated from the pollen grains not only the pollen DNA but also the bacterial DNA — the main genome as well as the episomal DNA — could be detected (fig. 8). Ripe pollen grains of N. glauca were germinated in germination medium containing 3H-labelled DNA from Rhizobium leguminosarum . DNA was isolated from the pollen material and fractionated by CsCl gradient centrifugation. The bacterial as well as the plant DNA were present in the gradient (fig. 9). All the experiments were carried out under semisterile conditions. To prevent bacterial growth the media contained a mixture of cloxacillin and ampicillin. Furthermore, the reisolation of the episomal DNA in the petunia experiments excludes any intensive bacterial degradation and reutilization of the labelled exogenous DNA respectively DNA building units. The results presented here could be relevant in two lines of investigations: 1. Unripe pollen grains could be incubated with exogenous DNA and than grown up to haploid, eventually genetically altered plants following the methods worked out by Nitsch (1974). 2. Ripe pollen grains could be germinated in exogenous DNA. Using this pollen material for fertilizations perhaps a DNA transfer from pollen to egg cell could be mediated. From the resulting seeds eventually genetically altered plants could be grown up (Hess, 1974). Pollen incubated with exogenous DNA could be used for normal fertilization and seed formation (Hess, in preparation; Hess et al., in preparation).

Fine structure of the pollen surface of some taxodiaceae and cupressaceae species

Fine structure of the pollen surface from five species of the Taxodiaceae family and one species of the Cupressaceae family was studied by scanning and transmission electron microscopy. All samples investigated have the same microverrucate sculpture. Sciadopitys is an exception, having a microechinate pattern.

Studies of Birch Pollen Antigens with Special Reference to the Allergenic principal

Abstract In the water-soluble protein fraction of birch pollen 10–15 antigens can be demonstrated by immunodiffusion techniques employing immune serum from experimental animals. Only one or two of these antigens are also highly allergenic in humans, i.e., responsible for the spontaneous sensitization which eventually leads to respiratory allergic symptoms. The highly allergenic antigens are physiochemically more stable, have a lower molecular weight (around 20 000) and are more rapidly released from the pollen grains than the other antigens. By immunofluorescence and micro-immunodiffusion methods, release of the allergens has been found mainly to occur through the pollen apertures. These and other findings suggest that the allergens are easily mobilized to the pollen surface from underlying primary locations. Transmucosally immunized rabbits produced skin sensitizing “reaginic” antibodies preferentially against the allergenic antigens, while the antigens with low or no allergenic activity were more immuno...

Demonstration of birch pollen allergen from isolated pollen grains using immunofluorescence and a single radial immunodiffusion technique.

Immunofiuorescence (IF) and single radial immunodiffusion (SRID) methods were modified in order to study the relation of allergen to the surface of birch pollen. By absorption of the anti-birch pollen sera employed, it was ascertained that both methods demonstrated thermostable allergenic birch pollen antigen and not nonallergenic antigens. The allergen rapidly diffuses from unfixed, wetted grains. After an aldehyde treatment and wet heating of the grains this leakage which mainly occurs through the pollen apertures was not demonstrated. Birch pollen allergen was released in a similar way from pollen of all of the six tested species of birch.

ELECTRON MICROSCOPICAL OBSERVATIONS ON POLLEN GRAINS OF SOME GRASS SPECIES

The ultrastructure of the pollen surface of fourteen grass species was investigated by studying carbon replicas and ultrathin sections. From the micrographs it was concluded that the investigated grasses can be divided into four groups according to the sculpture types of their pollen surface. One of these types appeared to occur in more than half of the grass species. Two spatial replicas of pollen grains justified the opinion that the shape of the pollen grains of grasses has value for pollen identification. It was concluded that for the identification of grass pollen electron microscopy is of less value than light microscopy.

Exine and the Role of the Tapetum in Pollen Development

CYTOCHEMICAL investigations and examination by electron microscopy of developing anthers in Tradescantia bracteata reveal that exine proper develops at a time when the microspores are separated from the tapetum by the callose walls of the tetrad. The bulk of exine is produced at an early stage, and at the time of release of microspores from the tetrads it has attained a pattern very similar to that seen at maturity. We have found no evidence to support the view that sporopollenin is produced by mitochondria1, nor have we observed Ubisch bodies or sporopollenin deposits in the tapetum of this plant at any stage, as have been reported in a number of other species1–3. Six days after break-up of the tetrads, when the deposition of intine has begun, channels 20–40 mµ in diameter can be seen traversing the endexine from the pollen surface to the intine. Between the intine and endexine, tubular structures believed to be sites of sporopollenin polymerization can be seen in a plane perpendicular to the long axis of the pollen grain. In tangential sections through the exine itself it often appears split into parallel bands of fibrils again perpendicular to the long axis of the pollen grain (Fig. 1a and b).

花粉表面の微細模様と二•三の術語の問題

花粉表面の微細模様と二•三の術語の問題

The use of surface samples in quaternary pollen analysis

Much of the uncertainty in the interpretation of Late Quaternary pollen assemblages can be removed by the judicious use of pollen surface samples from a variety of vegetational formations. The technique is especially useful in new regions of investigation, where not much is known of the pattern of the pollen sequence, and it can even be used in regions where much of the vegetation is disturbed. Two scales of study can be applied: 1. (1) For a regional study in a forested area, samples are taken from the centers of relatively large lakes, so that the regional pollen rain will not be distorted by local pollen rain. The regional pollen rain may then be compared with the regional upland vegetation, as surveyed by standard phytosociological methods, including air-photo study. A very large area must be surveyed, especially if the upland vegetation consists of a species-rich mosaic of forest types in an area of diversified topography. 2. (2) A second type of surface-sample study provides a different basis for historical reconstructions. In this case, transects of surface samples are taken in each of the main forest types, extending from the centers of small ponds or bogs to the adjacent hill slopes. Detailed vegetational analysis must be made of all the plant associations crossed by the transects from lowland to upland, and in the pollen analysis particular attention must be paid to the herbaceous pollen types. In this way the pollen counts can be assigned to either local, extralocal, or regional vegetation. Characteristic local or extralocal pollen percentages may then be identified in a pollen diagram for a long core from a small pond or bog, in order to work out the local vegetational succession that either accompanied or was independent of changes in the climatically controlled regional vegetation.

Stevens Pond: A Postglacial Pollen Diagram from a Small Typha Swamp in Northwestern Minnesota, Interpreted from Pollen Indicators and Surface Samples

The pollen assemblages of a core in the coniferhardwood formation in northwestern Minnesota are compared with the floristics of the recent vegetation in the region. Percentage levels of the main tree components have been compared first with those from recent surface samples taken at the same short distance from various types of upland forests and second with the regional values of the pollen rain in this area (McAndrews 1966). To that end all the data were recalculated on the basis of special pollen sums. The regional diagram of Stevens Pond shows basically the same assemblage zones as established by McAndrews but without the late-glacial Picea-Populus assemblage zone. The pollen in the following Pinus-Pteridium assemblage zone has been interpreted as derived from a pine forest. During the midpostglacial expansion of the prairie eastwards the regional vegetation must have been a Quercus savanna, locally with prairie. Corylus reaches relatively high percentages in this zone. Among the prairie elements especially the occurrence of Lilium philadelphicum may be noted. In the next zone the pollen diagram shows a rise of the curves of mesic elements. In spite of this the comparison with recent surface samples indicates a xerophytic Quercus forest rather than a mesophytic deciduous forest. In the following Pinus assemblage zone pine was present along the margin of Stevens Pond and is therefore overrepresented in the diagram. In the uppermost zone the pollen curves show the effect of logging of the forest about 1900. Pollen of cultivated and introduced plants appear in this zone. Many local pollen types were found, on account of local overrepresentation. This made it possible to compare the local Stevens Pond sequence with the composition of recent lowland vegetation types. The pollen sequence was similar to a large extent to the recent pattern of lake filling, starting with a eutrophic vegetation of Typha latifolia and Salix in the prairie period and leading to a Larix forest and then to a mesotrophic Picea mariana forest, the present edaphic climax on peaty soils. There is a delay, however, in the introduction of acidophilous species, the Larix forest being without Sphagnum and Ericaceae. This is explained by assuming an influence of the vegetation of the surrounding slopes upon the local vegetation. About 1900 the bog forest was destroyed by logging operations and replaced by the present Typha latifolia mat.

The Electron Microscopy of Pollen and Spore Surfaces

The Electron Microscopy of Pollen and Spore Surfaces

‘LO-Analysis’ as an Aid in the Study of Fungal Spore Morphology

ERDTMAN1 defined LO- analysis as : “the different patterns of pollen or spore wall surfaces … recorded as they appear at successive adjustments of the microscope.”