Parallel instrumentational approaches to the study of the bioenergetics of photosynthesis in chloroplasts and intact plants
Kramer, David Mark
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Permalink
https://hdl.handle.net/2142/21012
Description
Title
Parallel instrumentational approaches to the study of the bioenergetics of photosynthesis in chloroplasts and intact plants
Author(s)
Kramer, David Mark
Issue Date
1990
Department of Study
Biophysics and Computational Biology
Discipline
Biophysics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Electronics and Electrical
Biophysics, General
Biology, Plant Physiology
Language
eng
Abstract
The intent of this research was the development and use of parallel instrumentation for the study of the bioenergetics of photosynthesis in in vitro and intact plant systems. To this end, three instruments have been developed and employed. Two highly sensitive, double-flash spectrophotometers based on that suggested by Joliot and Joliot (1984) have been constructed for use in measuring flash-induced absorbance changes in photosynthetic systems. The utility of the laboratory-based instrument is demonstrated through investigations of the electron transfer kinetics and static midpoint potentials of the chromophores of the cytochrome b6f complex (b6f) under a variety of redox and inhibitory conditions designed to help elucidate its function in electron transfer. These studies, were directed at settling controversies about the properties and function of the chloroplast cytochrome $b\sb6/f$ complex, including the redox chemistry of the two b-cytochrome, the relative rates of reduction of cytochrome b and cytochrome $f$, and the role of the $b\sb6/f$ complex in cyclic electron flow. The results of these studies were in agreement with a Q-cycle mechanism for the cytochrome $b\sb6/f$ complex. The field-portable version of the spectrophotometer demonstrated by observation of the electron transfer kinetics through cytochrome $b$ and $f$ and by observing the flash-induced electrochromic shift in intact leaves. It was also utilized to study the regulation of the chloroplast F$\sb0$-F$\sb1$-ATP synthase or coupling factor (CF) in leaves of intact plants. These studies were extended to the field where the regulation of the CF under low light levels at sunrise were observed. The third instrument developed was designed to measure the donor and acceptor reaction of photosystem 2 (PS2) in leaves of intact plants. This instrument, named the multi-flash kinetic fluorimeter, is an improved version, designed for use on intact plants, of the double-flash kinetic fluorimeter already in use on isolated chloroplasts in this and many other laboratories. The instrument allows much more rapid and convenient measurements than previously possible. It is demonstrated by observations of the effects on flash-induced fluorescence yield changes, of the turnover of the oxygen evolving complex and the two-electron gate. (Abstract shortened with permission of author.)
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