Björn Walles

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Although intact pollen grains are assumed to be the primary carrier of pollen allergens, specific immunoreactive components have been found in other aerosol fractions, e.g., starch grains and remains of tapetal cells Cryo-scanning-electron-microscopy results demonstrate the presence of a clear network of strands connecting the tapetum with the microspores.(More)
 The ultrastructure of egg cells in Abies alba was examined to elucidate the lack of maternal inheritance of plastids. Before fertilization, maternal plastids are absent in the perinuclar zone containing mainly mitochondria and smooth endoplasmic reticulum. During egg cell development the maternal plastids are transformed into large inclusions which are(More)
The normal ultrastructural changes during the cell cycle have been studied in synchronized cultures ofScenedesmus obtusiusculus Chod. grown in a complete nutrient solution. The interphase cell has a three-layered wall, an oblong chloroplast with a central pyrenoid, a dictyosome associated with the nuclear envelope and surrounded by a cylinder of endoplasmic(More)
For this work we have used various microscopical methods (LM, SEM, and TEM) to study pollen tube growth and interaction with the transmitting tisse inStrelitzia reginae, which has an open style. By the use of SEM it was possible to trace the exact route of the pollen tubes in the ovary of this plant and demonstrate that they exclusively follow the outlines(More)
This investigation concerns a unique type of epidermal cells in the anther ofStrelitzia reginae. At dehiscence these cells are released and form multicellular threads. The radial and tangential middle lamella regions of their cell walls disintegrate by the formation of numerous growing and fusing cavities. The possibility that this process could be due to(More)
Placental cells in the ovarian transmitting tissue ofLilium spp. are organized as transfer cells with inbuddings facing the ovarian locule. A detailed analysis of microtubule (MT) organization during development of these polarized cells is reported here. Formation of wall projections occurs at the apical part of the cell starting on the day of anthesis, and(More)
In the cambial region ofSalix dasyclados plants, extensive spherical formations of myelin-like lamellar configurations were found during the transit period between winter dormancy and reactivation of growth in early spring. The lamellar structures occurred in parenchyma cells containing tannins and were associated with spherosomes. Cytomembranes in(More)
The effect of various factors interacting with cell division and/or growth (cold, heat shocks, Ca 2+, p3-, hormonal starvation, microtubular poissons, DMSO) has been followed to increase the synchrony of cell life events of tobacco cell culture. The model strain VBI-O, exhibiting highly polar cell division and growth (Opatrn~ and Opatru~i 1972, Z~imalovh et(More)
Placental cells line the ovarian transmitting tract inLilium regale and produce exudates for secretion. Sections through the highly lobed nuclei of these cells reveal the presence of membrane profiles which form vesicles with varying dimensions in cross section. Computer reconstruction of the nucleus reveals that the vesicle profiles form a complex(More)