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  • 1
    ISSN: 1615-6110
    Keywords: Lamiaceae ; Salvia verbenaca ; Dichogamy ; protandry ; pollination ; self-fertilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Though dichogamy is generally interpreted as a means of preventing self-fertilization, the efficiency of this mechanism has been questioned. Little attention has been paid to functional aspects of male/female timing, such as variation over time in pollen germinability and in stigma receptivity. In the present study these aspects of male/female timing were investigated in the protandrous speciesSalvia verbenaca. To evaluate the effects of selfing, fruit set, total seed weight produced and seed/ovule ratio were also determined, (a) following artificial crossing, (b) following selfing (i.e. bagging) and (c) under natural conditions. Both pollen germinability and stigma receptivity peaked on the last day (day 3) of the flower's life, which presumably favours selfing. Neither fruit set nor seed/ovule ratio were significantly affected by pollination regime, but the total seed weight produced by artificially crossed plants was significantly higher than that produced by bagged or untreated plants. Neither fruit set, seed/ovule ratio nor total seed weight differed significantly between the two years of study. Thus, if aS. verbenaca flower receives outcrossing pollen it will produce a greater weight of seeds (with consequent advantages in terms of female reproductive success). However, the peaking of both pollen germinability and stigma receptivity on day 3 of the flower's life means that selfing is likely to occur if outcrossing pollen has not been received over the early part of the flower's life.
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  • 2
    ISSN: 1615-6110
    Keywords: Fabaceae ; Anthyllis vulneraria ; Fruit-set ; seed weight variation ; resource allocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fruit-set and seed weight variation was studied in a population ofAnthyllis vulneraria subsp.vulgaris (Fabaceae) in northwestern Spain. The plants produce several shoots, each bearing two to four inflorescences that open one at a time from bottom to top. Fruit-set, seed-pod weight and seed weight were found to be significantly higher in proximal inflorescences than in distal inflorescences of the same shoot; mean seed weight was up to three times higher in proximal than in distal inflorescences. By contrast, none of the three variables varied significantly among plants or among shoots of the same plant. Similarly, none of the three variables differed significantly between early- and late-flowering plants, or between plants monitored in 1993 and in 1994. These results are compatible with the view that shoots function as semiautonomous units as regards resource allocation, and that within the shoot resources are preferentially allocated to proximal (= early-opening) inflorescences. In the plants studied, the ratio of seed-pod weight to seed weight was fairly constant, suggesting that the pod is important for seed success.
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  • 3
    ISSN: 1432-203X
    Keywords: Citrus sinensis L. Osbeck cv. Pineapple ; Sweet orange ; Agrobacterium tumefaciens ; Genetic transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Transgenic sweet orange (Citrus sinensis L. Osbeck) plants have been obtained by Agrobacterium tumefaciens-mediated gene transfer. An hypervirulent A. tumefaciens strain harboring a binary vector that contains the chimeric neomycin phosphotransferase II (NPT II) and ß-glucuronidase (GUS) genes was cocultivated with stem segments from in vivo grown seedlings. Shoots regenerated under kanamycin selection were harvested from the stem segments within 12 weeks. Shoot basal portions were assayed for GUS activity and the remaining portions were shoot tip grafted in vitro for production of plants. Integration of the GUS gene was confirmed by Southern analysis. This transformation procedure showed the highest transgenic plant production efficiency reported for Citrus.
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  • 4
    ISSN: 1573-9368
    Keywords: sweet orange ; Citrus ; woody ; transformation ; Agrobacterium ; mature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Regeneration and transformation systems from mature plant material of woody fruit species have to be achieved as a necessary requirement for the introduction of useful genes into specific cultivars and the rapid evaluation of resulting horticultural traits. We report here, for the first time, a procedure for genetic transformation and regeneration of mature tissues of woody plants that overcomes the long juvenile periods and high heterozygosity that are characteristic of most of these species. An improved regeneration frequency from mature explants was obtained by invigoration of the plant material through grafting of mature buds on juvenile seedlings. Co-cultivation of the explants in feederplates after inoculation with Agrobacterium tumefaciens resulted in enhanced transformation frequencies. Furthermore, in vitro shoot-tip grafting of the regenerated mature shoots on seedling rootstocks provided a rapid and efficient system for plant production. Citrus is the most extensivel y grown fruit crop worldwide and sweet orange (Citrus sinensis L. Osbeck) accounts for approximately 70% of the Citrus total production. Mature transgenic sweet orange plants have been obtained, which flowered and bore fruit in 14 months
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  • 5
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Citrus trees have a long juvenile phase that delays their reproductive development by between 6 and 20 years, depending on the species. With the aim of accelerating their flowering time, we transformed juvenile citrus seedlings to constitutively express the Arabidopsis LEAFY (LFY) or APETALA1 (AP1) ...
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Archive for history of exact sciences 53 (1998), S. 147-180 
    ISSN: 1432-0657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Natural Sciences in General
    Notes: Abstract It is generally accepted that, around the turn of the century, GIBBS and EINSTEIN independently developed two equivalent formulations of statistical mechanics. GIBBS version is taken as genuine and rigorous, while EINSTEINs, despite some features which are characteristic of him, is usually considered a not totally satisfactory attempt. It will be shown in the present work that such a picture is oversimplified and requires further nuancing. In fact, there are significant differences, with important implications which have not been sufficiently examined, between the two formulations. Several issues relating to the impact of the two versions will also be addressed.
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  • 7
    Electronic Resource
    Electronic Resource
    Copenhagen : Munksgaard International Publishers
    Centaurus 42 (2000), S. 0 
    ISSN: 1600-0498
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Centaurus 34 (1991), S. 0 
    ISSN: 1600-0498
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Natural Sciences in General
    Type of Medium: Electronic Resource
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