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  • 1
    ISSN: 1615-6102
    Keywords: Adventive embryos ; Coriander ; Expiants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The petiole expiants of coriander when cultured on a solid or liquid Murashige and Skoog's medium supplemented with 0.5 mg/l 2,4-D developed a large number of meristemoids. These meristemoids could then be induced to form adventive embryos when transferred into a liquid MS-medium without 2,4-D. The development of the expiants leading to the formation of meristemoids was followed anatomically and by using SDS-polyacrylamide gel electrophoresis of soluble proteins at various days of culture.
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  • 2
    ISSN: 1615-6102
    Keywords: Acid phosphatase ; Capsella ; Female meiocyte ; Ovule ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Pre-meiotic and prophase I ovules ofCapsella bursa-pastoris (L.) Medic.(monosporic,Polygonum type of gametophyte development) were fixed routinely or incubated in a modified Gomori medium containing β-glycerophosphate as a substrate. Prior to the beginning of meiosis the potential meiocyte is ultrastructurally similar to the other cells of the nucellus and is distinguished only by its size and position. At the initiation of prophase I dramatic ultrastructural and ultracytochemical changes take place in the female meiocyte. These include the sudden appearance of cytoplasmic structures composed of single and multiple concentric cisternae, distinctive changes in plastids and mitochondria, and the blebbing of 0.3 μm double-membraned vesicles from the nuclear envelope. The concentric cisternae encapsulate portions of cytoplasm containing ribosomes, plastids, mitochondria, ER fragments and vesicles. Both single and multiple concentric cisternae localize high levels of acid phosphatase and function as autophagic vesicles (AVs) that sequester ribosomes and organelles for destruction during meiosis. Plastids stop dividing and become more spherical during prophase I. Some plastids localize acid phosphatase and many show continuities between the outer membrane and the plastid envelope and acid phosphatase-rich RER cisternae. Mitochondria appear as dense, contracted spheres or rods. Some mitochondria localize acid phosphatase but they do not show membrane confluencies with the ER. Some of the plastids and mitochondria that are segregated into the functional megaspore at meiosis II are destroyed but others apparantly survive meiosis and give rise to the plastid and mitochondrial populations of the young gametophyte (Schulz andJensen, unpublished). The lateral and end walls of the meiocyte show patches of intense aniline blue fluorescence and the chalazal end wall of the cell is perforated with large numbers of plasmodesmata.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 107 (1981), S. 255-267 
    ISSN: 1615-6102
    Keywords: Chara ; Charasome development ; Coated membrane vesicles ; Endocytosis ; Nitella ; Plasmalemma invaginations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We report on an unusual phenomenon which occurs in some characean algae as a normal plasma membrane activity and also in association with charasome formation. The phenomenon of formation of coated invaginations of the plasma membrane was observed in twoChara and 6Nitella species. These invaginations are coated on their cytoplasmic surface, are 50–60 nm in diameter and rarely exceed 60 nm in length. They are abundant in the young cells ofChara andNitella and also occur in mature cells, but at a lower frequency.N. translucent is an exception in that coated invaginations were few in the young cells and absent in mature cells. Coated vesicles (50–60 nm diameter) were closely associated with these invaginations. Our observations suggest the vesicles may be derived from the invaginations by endocytosis. A close relationship was noted between the development of charasomes (plasmalemma modifications) and coated invaginations. Numerous coated invaginations are seen along the membranes of young charasomes; these invaginations appear to be associated with growth of the charasomes. Coated vesicles were not associated with the coated invaginations of the charasome membrane. The tubular network of cytoplasm and wall space seen in the mature charasome may be formed by fusion of coated invaginations of the developing charasomes, leaving cytoplasmic strands between the fused portions. Coated invaginations were not present along charasomes of the mature cells.
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  • 4
    ISSN: 1615-6102
    Keywords: Fungal spore walls ; Spore surface ; Spore germination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Dormant sporangiospores ofSyncephalastrum racemosum have a regular pattern of rodlets on their surface. During the spherical growth phase of spore germination these rodlets become displaced and areas free from rodlets appear. At the time of germ tube emergence the rodlets remain on the spherical portion of the spore whilst the germ tube has a smooth surface.
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  • 5
    ISSN: 1615-6102
    Keywords: Asci ; Ascomycetes ; Ascogenous hyphae ; Croziers ; Intercellular communication ; Septal pores ; Sordaria humana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Septal pores and associated structures have been studied in ascogenous hyphae, croziers and asci ofSordaria humana by means of electron microscopy of serial and random sections. Pores exhibit variable structures from relatively simple pore caps to complex swollen rims with associated membrane cisternae. The simple types are found at the base of the ascogenous hyphae while the complex forms occur at the apex, in the croziers and in very young, presporulation asci. Post-sporulation asci contain a relatively simple type of pore structure. Cells which subtend the ascogenous hyphae exhibit both open and capped pores in their cross walls. Pore structures may be asymmetric in which case they show greater complexity on the side of the cross wall nearest to the apex or crozier. Membranous components of the complex pores are continuous with the endomembrane systems of the two adjacent cells and thus with the outer membranes of the nuclear envelopes. Membrane continuities may connect prefusion nuclei or fusion nuclei in penultimate cells, with nuclei of the stalk and terminal cells of croziers. Some speculation is presented as to the implication and possible roles of these structures in relation to cell differentiation within the ascogenous hyphae and croziers.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 107 (1981), S. 161-169 
    ISSN: 1615-6102
    Keywords: Adhesiveness ; Amoeba ; Cell surface state ; Endocytosis ; Reflection interference contrast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The adhesive behaviour ofAmoeba proteus during induction of endocytosis has been studied with interference reflection microscopy. Although phagocytosis and pinocytosis, jointly termed endocytosis, are closely related phenomena, it was found that the way they affect adhesiveness of amoebae differs substantially. Phagocytosis is accompanied by an increase in area of cell surface contacting the substratum, whereas during pinocytosis a sharp decrease of contact area is observed. The resistance to detachment increases in prey-stimulated and phagocytosing amoebae but declines as the pinocytosis is being induced. These results suggest that the influence of the induction of phagocytic activity on the cell periphery differs from that of induction of pinocytosis.
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  • 7
    ISSN: 1615-6102
    Keywords: Breeding system ; Heterostyly ; Pollen-stigma interaction ; Pollen tube growth ; Primula ; Self-incompatibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The stigmas of the heterostylous genusPrimula are of the “dry” type without a free-flowing surface secretion. The papillae of the stigma surface cells of the two morphs, in pin (stigma exserted) and thrum (stamens exserted), bear a thin proteinaceous surface pellicle, overlying a discontinuous cuticle. The vacuoles of the papillate cells contain tannins, and tannin cells extend in files through the stigma heads and form a loose sheath surrounding the pollen-tube transmitting tract in the styles. The cells of the transmitting tissue in the stigma heads have a normal complement of organelles, and abundant ribosomal endoplasmic reticulum. The intercellular spaces contain an internal secretion which reacts cytochemically for both carbohydrate and protein. The transmitting tract in the styles forms a central core surrounded by several vascular strands. The cells are elongated, and the intercellular spaces here also have a carbohydrate-protein content. In a compatible pollination, thrum pollen tubes enter the stigma by penetrating the cuticle at the tip or on the flank of the pin papilla. Pin tubes on the thrum stigma enter between adjacent papillae, penetrating the thin cuticle at the base. The tubes grow through the transmitting tracts in the intercellular material.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 107 (1981), S. 189-194 
    ISSN: 1615-6102
    Keywords: Haemanthus katberinae Bak ; Induction ; Chromosome condensation ; Mitosis ; Time-lapse cinematography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The presence of a prophase nucleus inHaemanthus endosperm happens to trigger the break down of the nuclear envelope in any interphase nucleus, located in its close proximity. Besides, chromosomes in the interphase nucleus start condensing gradually for the initial breaking point which is the nearest point to the prophase. The observation suggest the diffusion of an inducer, whose progression has been recorded to occur at a rate of 1.1 μm/min.
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  • 9
    ISSN: 1615-6102
    Keywords: Bentazon ; Chloroplast adaptation ; Grana development ; Plastoglobuli ; Raphanus sativus ; Stacking degree
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ultrastructure of chloroplasts from radish seedlings (Raphanus sativus L.) grown at high (24 klux; 250 W · m−2) and at low-light quanta fluence rates (1 klux; 15W · m−2) exhibits differences in many structural parameters. 1. The low-light (shade-type) chloroplasts are characterized not only by higher grana stacks and a higher stacking degree of thylakoids, but also by broader grana than the high-light (sun-type) chloroplasts. The latter are larger (length and width), possess large starch grains and contain more and larger plastoglobuli than the shade-type chloroplasts of the low-light plants, which are lacking starch. 2. The photosynthesis herbicide bentazon (10−4M) induces a shade-type adaptation (broader and higher grana stacks, higher stacking degree) particularly at high and to some extent also at low-light quanta fluence rates. The starch content and the number of plastoglobuli in the high-light bentazon chloroplasts is reduced as compared to the high-light controls.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 107 (1981), S. 235-254 
    ISSN: 1615-6102
    Keywords: Cup-shaped coated vesicles ; Exocytosis ; Digestion ; Discoidal vesicles ; Intracytosis ; Ophrydium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Digestion in the peritrich ciliateOphrydium versatile O.F.M. involves a complex sequence of intracytotic and exocytotic membrane fusion and recycling events. Food particulates are concentrated in the lower cytopharynx which forms a fusiform-shaped food vacuole. Upon release from the cytopharynx, this food vacuole begins to condense, concentrating the food particulates. Excess membrane is removed intracytotically. These released membranes pieces form discoidal vesicles which are recycled to the base of the cytopharynx, thus providing additional membrane for subsequent food vacuole formation. In the condensed food vacuole, digestion proceeds; hydrolytic enzymes are delivered to the food vacuole via rough endoplasmic reticulum and/or by the cup-shaped coated vesicles (CSCV). As these vesicles fuse with the food vacuole, the food vacuole enlarges, digestion proceeds and an electron-dense membrane coat appears along the luminal surface of the food vacuole. Prior to defecation, the food vacuole undergoes a final condensation; irregularly-shaped, electron dense, single-membrane bound vesicles are cut-off intracytotically from the old food vacuole. These vesicles undergo condensation and invagination to form the cup-shaped coated vesicles (CSCV) which fuse with younger food vacuoles.
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