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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 1 (1988), S. 1-2 
    ISSN: 1432-2145
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2145
    Keywords: Pollen tube ; Organelle movement ; Actin microfilament bundles ; Iris pseudacorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Continuous observation of organelles and other cytoplasmic inclusions in the older stretches of living pollen tubes of Iris pseudacorus shows that in the more attentuated parts of the protoplast they move along single, mainly longitudinally oriented fibrils, corresponding to those previously isolated from other species and shown to contain bundles of uniformly polarised actin microfilaments. The traffic associated with each fibril is unidirectional, but organelles move along them independently, sometimes with conspicuously different velocities. Larger columns of cytoplasm passing along the tube are associated with several such fibrils, as revealed in occasional discontinuities and also in columns isolated from the tube in suitable medium without fixation. The dimensions of the individual fibrils suggest that the bundles of actin microfilaments are not likely to be enclosed in a unit membrane corresponding to a tonoplast. If so, the nature of the continuous cavities traversed by numerous fibrils in the older parts of the pollen tube requires reappraisal, since these are more likely to be volumes of attentuated cytoplasm comparable with that of the central cavity of the sieve tube than vacuoles of the normal plant-cell type.
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  • 3
    ISSN: 1432-2145
    Keywords: Self-incompatibility ; Gramineae ; Two loci system ; Phalaris coerulescens ; Stigma proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Protein extracts from four self-incompatible genotypes of Phalaris coerulescens were subjected to analysis by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and ultra-thin isoelectric focusing. A comparison between stigma, root and leaf extracts showed that there was no significant difference in electrophoretic or isoelectric focusing patterns between the genotypes for both root and leaf proteins. However, stigma protein patterns did vary between genotypes especially within the molecular weight region of 43 000–97 000 and within the pI range 5–7. The stigma-specific changes strongly suggest a link between the self-incompatible genotype and these stigma proteins. However, because there are two loci involved, it is not yet possible to precisely assign particular proteins to each S- or Z-allele.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 1 (1988), S. 32-35 
    ISSN: 1432-2145
    Keywords: Self-incompatibility ; Classical model ; Heterosis model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An alternative to the classical model of self-incompatibility indicates that genetic control of self-incompatibility could involve more than one locus and function through passive failure of incompatible pollen tubes rather than through their active inhibition. Both aspects of the alternative model have been tested and, in each case, the data support the classical single-locus oppositional interpretation rather than the alternative. On the basis of these data, and others now available, we conclude that, in the Solanaceae, and presumably also in some others, self-incompatibility is better explained by the classical interpretation. Several points, however, remain to be resolved.
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  • 5
    ISSN: 1432-2145
    Keywords: Agglutinins ; Chlamydomonas ; Circadian rhythm ; Flagella ; Gametes ; Receptors(mating)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We describe a circadian rhythm in the surface density of receptors that play a dominant role in the mating process of the unicellular green alga Chlamydomonas eugametos.These receptors — called agglutinins — are large glycoproteins extrinsically bound to the membrane of gamete flagella. We found circadian fluctuations in their density. Since inhibition of protein synthesis affected the agglutinin density without a lag period at any time,we conclude that the density was dependent on de novo synthesis and that the fluctuations in density are caused by circadian oscillations in the rate of agglutinin synthesis. This phenomenon evidently underlies the pronounced endogenous rhythm in mating competence that we described previously (Demets et al. 1987). Finally, we speculate on the nature of the time keeping mechanism that is generating these rhythmic events.
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  • 6
    ISSN: 1432-2145
    Keywords: Heterosis ; Polygenes ; Size ; Ecballium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Statistical analysis was performed on a set of samples cultivated in balanced, incomplete blocks corresponding, respectively, to filial generations (pure, hybrid or backcross) distinguishable in the hybridization between the monoecious and dioecious subspecies of Ecballium elaterium (L.) Rich. We thus analyzed the possible existence of polygenes that condition the size of the plants, in particular the most observable characteristic effect of the polygenes, i.e., heterosis or hybrid vigor. The experimental results show that heterosis exists with respect to size of the individual plant. The occurrence of this phenomenon provides experimental evidence for the existence of a system of polygenes that affect this property. With respect to each of these polygenes, the genotype of each subspecies contains different alleles. This system of polygenes very likely plays a role in the phenotypic modification which, regarding the sex of the plant itself, has been recognized and confirmed previously.
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  • 7
    ISSN: 1432-2145
    Keywords: Helleborus foetidus ; Galanthus nivalis ; Pollen-grain and pollen-tube permeability ; Generative cell wall ; Generative cell permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The permeability of pollen grains, pollen tubes and generative cells of Helleborus foetidus and Galanthus nivalis has been investigated using four probes spanning a wide range of molecular weights: 4,6-diamidino-2-phenyl indole (DAPI; mol.wt. 350). Evans blue (mol.wt. 960), FITC-dextran (average mol.wt. 19400) and FITC-albumin (average mol.wt. 67000). DAPI penetrated into the vegetative cells of desiccated and hydrated pollen, and also entered growing pollen tubes. In contrast, the generative cells of hydrated pollen and of pollen tubes were highly resistant to penetration, as they were when isolated in osmotically balancing medium. Evans blue failed to enter intact generative cells under any of the conditions tested. The dye ultimately entered the vegetative cells of some pollen grains, but these were non-germinable. Growing pollen tubes invariably resisted penetration. Neither of the high molecular weight conjugates entered germinable pollen grains or intact pollen tubes. The results suggest that it is highly unlikely that DNA fragments of high molecular weight can enter viable pollen, pollen tubes or generative cells under any normal conditions.
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  • 8
    ISSN: 1432-2145
    Keywords: Cytoskeleton ; Embryo sac development ; Megasporogenesis ; Microtubules ; Gasteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using immunocytochemical techniques, tubulin distribution in various stages of meiosis and embryo sac development was studied. In the archespore cell some microtubules appeared to be randomly oriented. During zygotene and pachytene, when the cell volume increases, a large number of microtubules in dispersed configurations and bundles were observed. During this stage the nucellar cells divide, and their parallel cortical microtubules play an important role in preparing the direction of cell enlargement. The protoderm cells show anticlinal-directed cortical microtubules. It can be concluded that the enlargement of the meiocyte during these early meiotic stages is influenced both by its own cytoskeleton and by growth of the nucellus. Thereafter, the microtubules function directly in meiosis and disappear for the greater part until the two-nucleate coenocyte is formed. In a four-nucleate coenocyte microtubules reappear around the nucleus; in a young synergid, randomly oriented microtubules are involved in cell shaping during the formation of the filiform apparatus; in the synergids of the mature embryo sac, many parallel arrays of microtubules are present. Microtubules are less abundant in other cells. It is concluded that the cytomorphogenesis of the developing coenocyte and embryo sac are due to cell growth of the nucellar cells together with vacuolation of the coenocyte.
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  • 9
    ISSN: 1432-2145
    Keywords: Generative cell ; Isolation ; Scanning electron microscopy ; Immunofluorescence ; Video-enhanced microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Generative cells were isolated from the pollen grains of three angiosperm species by a method similar to that previously reported for Haemanthus katherinae (Baker). Both the external appearance and the internal structure of the isolated generative cells were observed by light and scanning electron microscopy. The dynamic changes occurring in the cells after they had been liberated from the pollen grains were recorded by video-enhanced microscopy. The distribution of microtubules in the isolated cells was revealed by immunofluorescence.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 1 (1988), S. 132-139 
    ISSN: 1432-2145
    Keywords: Liliaceae ; Tulipa cv. ‘Apeldoorn’ ; Sporopollenin biosynthesis ; Tracer experiments ; Degradation of labeled sporopollenin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Extensive tracer experiments were carried out on Tulipa with the aim of determining the structure and biosynthesis of sporopollenin. The radiolabeled precursors were applied using an improved technique previously selected. The sporopollenin fraction was purified using either a gentle method — hydrolyzing enzymes (pronase, amylase, amyloglucosidase, cellulase, pectinase and lipase) and alkaline hydrolysis (method A) — or by a conventional aggressive procedure, where the material was enriched by alkaline hydrolysis and treated several days with 80% phosphoric acid (method B). The 14C-labeled precursors applied were mevalonate, glucose, acetate, malonic acid, phenylalanine, tyrosine, p-coumaric acid. Regardless of the method of enrichment, a higher level of incorporation into the sporopollenin fraction was always seen with [U-14C]-phenylalanine. The level of radioactivity found in sporopollenin labeled by phenylalanine or malonate was sufficiently high for the labeled polymer to be degraded and the products released analyzed for the first time. In the case of phenylalanine-labeled sporopollenin, the main degradation component, p-hydroxybenzoic acid, was also the most heavily labeled substance. This result was not dependent on the procedure used for sporopollenin enrichment. These findings are interpreted as meaning that phenylpropane metabolism via phenylalanine-ammonia lyase is involved in sporopollenin biosynthesis.
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