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  • 1
    Electronic Resource
    Electronic Resource
    Investigation of the microphase separation transition in low-molecular-weight diblock copolymers (1989)
    s.l. : American Chemical Society
    Macromolecules 22 (1989), S. 3380-3387 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00198a032
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Postpollination-prezygotic ovular secretions into the micropylar canal inPseudotsuga menziesii (Pinaceae) (1996)
    Springer
    Journal of plant research 109 (1996), S. 147-160 
    Details
    ISSN: 1618-0860
    Keywords: Female gametophyte ; Integument ; Ovule ; Pseudotsuga ; Secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ovular morphology was examined ultrastructurally inPseudotsuga menziesii to determine the effects of the ovule on pollen development. Vesicles containing lipid-like substances traverse cell walls of the inner epidemis of the integument and release their contents at the integument surface to form the integumentary membrane. A major aqueous secretion from the integument into the micropylar canal is proposed to occur by the movement of the integumentary membrane and its invaginations towards the center of the micropylar canal. The cellular degeneration of the nucellar apex results from the breakdown of vacuoles. After this degeneration, electron-dense substances move from the prothallial cells of the female gametophyte towards the nucellus, and many morphological changes in the nucellus, prothallial cells, and micropylar canal take place simultaneously. We interpret these changes to result from another major secretion from the prothallial cells. Egg cytoplasm appears to disorganize for a short time. Simultaneously, substantial amounts of electron dense-substances in the prothallial cells and lipid-like substances in surface cell walls of the female gametophyte move towards the nucellus as components of the third major secretion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02344540
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Western white pine (Pinus monticola Dougl.) reproduction: I. Gametophyte development (2000)
    Springer
    Sexual plant reproduction 13 (2000), S. 61-74 
    Details
    ISSN: 1432-2145
    Keywords: Key words White pine ; Pinus ; Megagametophyte ; Egg ; Microgametophyte ; Sperm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Male and female gametophyte development are described from light and transmission electron microscope preparations of ovules from first and second year Pinus monticola Dougl. seed cones. In the first year of development, pollen tubes penetrate about one-third the distance through the nucellus. The generative cell and tube nucleus move into the pollen tube. The megagametophyte undergoes early free nuclear division. First-year seed cones and pollen tubes become dormant in mid-July. In the second year, seed cones and pollen tubes resume development in April and the pollen tubes grow to the megagametophyte by mid-June. Early in June the generative cell undergoes mitosis, forming two equal-size sperm nuclei that remain within the generative cell cytoplasm. The generative cell has many extensions and abundant mitochondria and plastids. The megagametophyte resumes free nuclear division, then cell wall formation begins in early July. Cell wall formation and megagametophyte development follow the pattern found in other Pinaceae. Three to five archegonial initials form. The primary neck cell divides, forming one tier of neck cells. Jacket cells differentiate around each central cell. The central cell enlarges and becomes vacuolate; then vacuoles decrease in size and the cell divides, forming a small ventral canal cell and a large egg. Plastids in the central cell engulf large amounts of cytoplasm and enlarge. This process continues in the egg, and the peripheral cytoplasm of the egg becomes filled with transformed plastids. Mitochondria migrate around the nucleus, forming a perinuclear zone. The wide area of egg cytoplasm between these two zones has few organelles. A modified terminology for cells involved in microgametophyte development is recommended.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004970000042
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Seasonal occurrence of potential ice-nucleating bacteria on Douglas fir foliage and seed cones (1990)
    Springer
    New forests 4 (1990), S. 55-61 
    Details
    ISSN: 1573-5095
    Keywords: Pseudotsuga menziesii ; cone abortion ; seed orchard ; pollination ; ice nucleation ; bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Total bacteria and fluorescent Pseudomonas populations were monitored on buds, conclets and foliage in a Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) seed orchard in April 1986 and between October 1986 and May 1987, over periods that spanned two pollination seasons. Seasonal variation in bacterial numbers was observed, with the highest levels occurring in the late winter and early spring. Bacterial populations active in ice nucleation were found. Bacterial numbers during pollination were higher in 1986 than in 1987. Conclet abortion at pollination was also higher in 1986 (55%) than in 1987 (11%). A relationship may exist between bacterial populations and conelet abortion at pollination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00119590
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    Paper (German National Licenses)
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