Ultrastructural study of the relationship between generative and vegetative cells inMagnolia ×soulangeana Soul.-Bod. pollen grains

Summary InMagnolia ×soulangeana pollen grains the generative cell (GC) does not become totally free within the vegetative cell (VC), at least until the pollen tube emergence. Due to a deviation in its detachment process from the sporoderm, the opposing ends of the VC plasmalemma do not fuse themselves when the GC moves away from the intine. Consequently, the interplasmalemmic space surrounding the GC does not become isolated but rather maintains continuity with the sporoderm through a complex formation that we have called plasmalemmic cord. The real existence of this formation was confirmed through serial sectioning showing the plasmalemmic cord to consist of the VC plasmalemma. In its initial portion it is occupied by a reasonably accentuated wall ingrowth of the inner layer of the intine (intine 3). In the remainder portion, neither of the cytochemical tests used in this work have revealed the presence of a significant amount of wall material. However, ultrathin sections of samples processed either chemically or by cryofixation showed the existence of an intricate system of tubules and vesicles, some of which are evaginations of the VC plasmalemma. The hypothesis that the plasmalemmic cord may have a role in the complex interactions between the two pollen cells is discussed

Ultrastructural Cytochemistry of the Nucleolus in Rat Oocytes at the End of the Folliculogenesis

Various ultrastructural changes occur during follicular growth in the rat oocyte nucleolus. The nucleolus, which has a reticulated fibrillogranular structure at the primordial and primary follicle stages, becomes entirely compact and is made up of a conspicuous and homogeneous mass at the antral follicle stage. In order to define the nature and the functions of this homogeneous mass, cytochemical methods allowing detection of nucleic acids, proteins and lipids were performed at the light microscopic and ultrastructural levels. The results obtained suggest that this nucleolar mass is probably composed of acid proteins which are not silver stained. This proteinaceous mass could be a special kind of nucleolar secretion providing material for meiotic resumption in the oocyte. Cytochemical researches now in progress should supply new information concerning the exact nature and the role of the nucleolar compact mass, which is the essential nucleolar component at the antral follicle stage and which really plays a role in the nucleolus in the first stages of embryogenesis

Electricity production from lignocellulosic biomass by direct coupling of a gasifier and a nickel/yttria-stabilized zirconia-based solid oxide fuel cell: influence of the H2S content of the syngas onto performances and aging

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