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  • Life cycle diagram  (1)
  • Nopaline synthase  (1)
  • Springer  (2)
  • American Chemical Society
  • Blackwell Publishing Ltd
  • Wiley
  • 1985-1989  (2)
Collection
Publisher
  • Springer  (2)
  • American Chemical Society
  • Blackwell Publishing Ltd
  • Wiley
Years
  • 1985-1989  (2)
Year
  • 1
    ISSN: 1573-5052
    Keywords: Life cycle diagram ; Population growth ; Remote sensing ; Simulation ; Transition matrix
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A method is presented to study dynamics of plants that cannot be separated into individuals such as many grassland, salt marsh and tundra species. A virtual population is created by using a permanent transect line through the vegetation and ‘individuals’ are defined as the branch segments distal to the intercept with the transect line. Addition and loss of ‘individuals’ together with growth or shrinkage form the basis for constructing a size-structured transition matrix. A discrete-event simulation demonstrates that: 1) a virtual population of individuals grows at the same rate as the parent population; and, 2) size-structured transition matrices for a virtual population and parent vegetation have similar dominant and subdominant eigenvalues so a virtual population can be used to describe the dynamics of a parent vegetation. Dwarf birch, Betula nana L., was studied in the northern foothills of the Brooks Range, Alaska, by using photography to record branch intercepts along permanent transect lines. The distal branch segments constitute a virtual population of the parent vegetation. Transects were photographed in 1985 and again in 1986 and changes of branch segments were used to construct two transition matrices for shrubs with and without elevated fertilizer treatment. Analysis of the virtual populations suggests that although Betula nana may show increased branch growth with increased fertilizer, in the long run this shrub may decline in the tundra in response to such treatment.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1617-4623
    Keywords: Nopaline synthase ; Promoter ; Repeat sequences ; Ti plasmid ; Expression vector
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using a promoter expression vector system based on the tumor-inducing (Ti) plasmid of Agrobacterium tumefaciens, we have studied the molecular structure of the nopaline synthase (nos) promoter which is active constitutively in transformed plant tissues. The system uses the sensitive and reliable chloramphenicol acetyltransferase (CAT) assay for the analysis of promoter strength in plant cells. Two sets of mutants were generated by sequential deletion of the nos promoter region from both 5′ and 3′ ends. These promoter fragments were linked to the cat coding sequence within the expression vector. The strength of the mutant promoters was measured in transformed tobacco calli as CAT activity. 3′ deletions up to-17 bp did not significantly affect the promoter strength. Further deletions into the TATA box region reduced the promoter strength by about ten-fold. Analysis of the 5′ deletion mutants showed that an upstream region is required for the nos promoter activity in addition to the TATA box and CCAAT box regions.
    Type of Medium: Electronic Resource
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