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  • 1
    ISSN: 1432-2048
    Keywords: Key words: Cell division ; Cell extension ; Gibberellin ; Internode ; Mitotic cell size ; Pisum (internode development)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. This study analysed the dynamics of cell production and extension, and how these were affected by applied gibberellic acid (GA3), during internode development in dwarf peas (Pisum sativum L. cv. Meteor). Image analysis was used to obtain cell number and length data for entire cell columns along the epidermis, the two outermost cortical layers, and the pith, from internode 7, over a time period covering the whole of the internode's growth phase. For a few days following the inception of an internode at the shoot apex, little further growth occurred, and there was no significant effect of GA3 on cell division or cell extension. The subsequent growth of the internode was stimulated more than fourfold by GA3 as a result of the production of more than twice the number of cells, which were twice as long. At least 96.5% of the cells of the mature internode were actually formed within the internode itself during this period of growth, demonstrating that the internode cells themselves represent the morphogenetic site of response to GA3. Mitoses and cell extension occurred along the full length of the internode throughout its development. The daily changes in cell numbers were modelled by the Richards function, and manipulations of the fitted functions to reveal time trends of absolute and specific cell production rates were performed for each stem tissue. The increase in cell numbers in the +GA3 plants was brought about by an increase in the rate of cell production, over a shorter time interval; specific cell production rates declined continuously from initial rapid rates in the +GA3 epidermis and pith, but declined more slowly in the cortex. The control (−GA3) epidermis and cortex cells exhibited a constant specific cell production rate (i.e. purely exponential) for several days. Cell extension rates were calculated so as to compensate for the size-reduction effects of concurrent cell division. These calculations confirmed that `real' cell extension rates were higher in the +GA3 internodes. Models of the cellular controls of internode growth, based on the estimated dynamics of cell division and extension, are discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of science education and technology 1 (1992), S. 259-274 
    ISSN: 1573-1839
    Keywords: Educational software ; biophysics software ; physiological software ; bioengineering software ; Hodgkin-Huxley model software ; diffusion software ; single voltage-gated channel software
    Source: Springer Online Journal Archives 1860-2000
    Topics: Natural Sciences in General , Technology
    Notes: Abstract We describe a software library that we have developed to teach biophysics and physiology to undergraduate engineering and science students as well as to medical students. The library, which is under development, now includes software on: (1) the Hodgkin-Huxley model for excitation of action potentials in electrically excitable cells (such as nerve and muscle cells); (2) a random-walk model of diffusion; (3) single voltage-gated ion channels; (4) steady-state chemically mediated transport; and (5) macroscopic diffusion processes. The software is used in a variety of ways: as an integral part of lectures, as the basis of special sessions held in electronic classrooms, as a source of homework assignments, and for special projects defined by the students. We describe the software and some of the pedagogic methods we have used.
    Type of Medium: Electronic Resource
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