Gamal El-Ghazaly

Studies of the Development of Wheat (Triticum Aestivum) Pollen

Abstract The origin and formation of the pollen wall and Ubisch bodies of wheat (Triticum aestivum) have been investigate d. Two layers of callose surround the developing sporocyst: the first layer formed [MATTER UNCLEAR IN PDF FILE]e ual in distribution and is believed to push the sporocyst against the tapetum, while [MATTER UNCLEAR IN PDF FILE]second layer completely surrounds each cell and is believed to act as a temporary wall [MATTER UNCLEAR IN PDF FILE] cell develops. The pollen wall is initiated in conjunction with the plasma membrane. The plasma membrane protrudes toward the microspore coat and at the end of each protrusion there is a small patch of electron dense material that is the beginning of the probacules. The probacules continue to enlarge and the protectal fibrillar-reticulate pattern becomes evident. A trilamellar structure forms on the surface of the plasma membrane. Material deposited on this structure appears to be the beginning of the foot layer. Eventually the foot layer increases i...

Pollen morphology, floral microcharacters and taxonomy of the genus Baccharoides Moench (Vernonieae: Asteraceae)

Abstract There are at present 25 species and 26 infraspecific taxa recognized in the resurrected genus Baccharoides. Of these, 17 species and 16 infraspecific taxa are new combinations made in this paper. Full descriptions of the pollen characters of the genus as well as the floral microcharacters, synonymy and distribution are provided. Remarks on diagnostic features are also given for most taxa in a taxonomic note.

Re-evaluation of a neglected layer in pollen wall development with comments on its evolution

This study focuses on one particular layer of the pollen wall, which develops below the endexine in the free microspore stage and prior to the initiation of the intine. This membranous-granular layer (MGL) has been described by different terms in the literature and has often been interpreted either as part of the endexine, or the intine. During ontogeny, however, the granular material shows a development that is clearly distinct, both in timing and mode of formation, from the endexine as well as the intine. Its chemical composition is also characteristic; the MGL resists acetolysis. Our ontogenetic observations from four dicot and one monocot species are used to illustrate the systematically widespread occurrence of this wall layer, its ultrastructure and histochemistry, and its comparable nature throughout angiosperms.

Ontogeny of pollen wall of leontodon autumnalis (hypochoeridinae, compositae)

Abstract Several development stages of 3-colpororate, echinolophate pollen grains of Leontodon autumnalis L. were studied with light microscope, scanning and transmission electron microscopes. The pattern of the tectum is differentiated in most respects in the early tetrad stages, and completed before digestion of the special callosic envelope. Differentiation of foot layer, columellae and endexine formed from material deposited on membranous lamellae during the free microspore stages. An increases in the volume of the protoplast apparently affected an extreme reduction of the foot layer in the regions of lacunae. The oral part of the colpororate aperture, was found to consist of two elliptical endexinous ora (os I and os II). Each os is covered by a membrane. These membranes developed by separation of lamellae at the margin of the oncus. The oral part of the aperture was seen to be covered by a plug.

Locafization of the major allergen Bet v 1 in Betula pollen using monoclonal antibody labelling

Abstract The major allergen Bet ver 1 of Betula pendula (= B. verrucosa) pollen grains has been localized by gold labelling with monoclonal antibodies. The allergen is located predominantly in the starch grains and to a slight extent in the exine and intine. The possibility that environmental factors might influence the liberation of allergenic compounds present in birch pollen grains is discussed.

Pollen Morphology of Some Species of Euphorbiaceae

Abstract The present study shows and emphasizes the necessity of correlating LM, SEM and TEM observations for a valid morphological interpretation of pollen grains. Four different pollen types of some Egyptian species of Euphorbiaceae are described. The pollen grains of Jalropha glauca are inaperturate and show characteristic structure in the form of striated clavae. It seems that the sunken areas of the exine are real and are probably functioning for adaptation of volume changes. The pollen grains of Phyllanthus rolundifolius differ from those of Andrachne telephioides. The main difference concerns the size of pollen grains, the exine structure, as well as presence or absence of the exine sculpture. In the former species exine sculpture is lacking and the structure consists of rather thin tectum perforatum supported by comparatively long and thin bacula. The pollen grains of Andrachne telephioides are larger and the sculpture resembles a microreticulum with usually elongated lumina surrounded by perforat...

Pollen morphology and ultrastructure of Marathrum schiedeanum (Podostemaceae)

The Podostemaceae, or river-weeds, comprise 46 genera and 270 species of dicots and are the largest family of strictly aquatic angiosperms. Despite the large size, specialized habitats, and enigmatic morphology of the family, relatively little is known about the palynology of Podostemaceae. In the current paper, pollen morphology and ultrastructure of Marathrum schiedeanum are described. Pollen grains are relatively small, spheroidal, and tricolpate to spiraperturate. The exine has a microechinate ornament, a tectate-granular sexine and a relatively thick nexine in non-apertural regions, and a semitectate sexine and thinner nexine in apertural regions. Although aperture variation occurs in the family, this is the first report of the spiral aperture type in Podostemaceae. The spiraperturate condition appears to be derived in river-weeds, as does the granular pollen wall, which represents a reduction of the typical columellae found in eudicots.

Ultrastructural characteristics of Betula pendula tapetum and pollen grains after rapid freezing and freeze-substitution

Using rapid fixation and freeze substitution method, the ultrastructure of the cytoplasm, including the membrane system, of Betula pendula pollen is well preserved. The cytoplasm of Betula pollen appears compact and organelles such as Golgi and RER are not yet demonstrating any secretory activities. The cytoplasm streaming is not established because the pollen grains are not completely hydrated and the microfilaments are still polymerized in bundless. The cytoplasm of the generative cell is well preserved including the cell wall like structure and cytoskeletal complexes present in the cell. Moreover the application of rapid freeze fixation of microspores and pollen grains of Betula showed clear details of ultrastructure of the Zwischenkorper (Z) at the aperture sites and the Z-layer (ZL) between the apertures. They are mainly composed of dense helical units that extend from the plasmalemma. Rapid freezing improves to a great extent the fixation of the delicate cell structure of the tapetum. After freeze f...

A Study of Airborne Pollen Grains of Alexandria, Egypt

There is only one report available on the aerobiology of Alexandria which was published over 28 years ago by Saad (1958). Since that time, the vegetation and cultivation in the city of Alexandria and its surroundings have changed, mainly due to industrialisation and urbanization after clearing of vegetation. Besides, the methods of trapping atmospheric pollen have been improved during the last few decades.