Journal Article

Photosynthetic Parameters of Leaves of Wild Type and Cyt <i>b</i><sub>6</sub>/<i>f</i> Deficient Transgenic Tobacco Studied by CO<sub>2</sub> Uptake and Transmittance at 800 nm

Hillar Eichelmann, Dean Price, Murray Badger and Agu Laisk

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 41, issue 4, pages 432-439
Published in print April 2000 | ISSN: 0032-0781
Published online April 2000 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/41.4.432
Photosynthetic Parameters of Leaves of Wild Type and Cyt b6/f Deficient Transgenic Tobacco Studied by CO2 Uptake and Transmittance at 800 nm

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  • Molecular and Cell Biology
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Parallel measurements of CO2 assimilation and 800 nm transmission were carried out on intact leaves of wild type and cytochrome b6/f deficient transgenic tobacco grown at different light intensities and temperatures, with the aim to diagnose rate-limiting processes in photosynthesis and investigate their adaptations to growth conditions. Maximum CO2- and light-saturated photosynthetic rate, mesophyll conductance, assimilatory charge and specific carboxylation efficiency were determined from CO2 fixation measurements and postillumination P700 rereduction time constant was measured from the transient of the 800 nm signal. Results show that growth conditions continue to modulate the expression of genes in transgenic plants, interfering with the antisense modulation, but under all environmental conditions the antisense treatment to decrease Cyt b6/f complexes ensured that the control of electron/proton transport rate by proton backpressure on the PSI donor side was stronger than the control by electron backpressure on the PSI acceptor side. Coordinated control of gene expression and enzyme activation ensures that different parts of the photosynthetic machinery—components of the electron transport chain, ribulose-1,5-bisphosphate carboxylase/oxygenase, enzymes of the sucrose and starch synthesis chains—are synthesized more or less proportionally under different environmental conditions and in case of mild genetic interference.

Keywords: CO2 fixation; Cytochrome b6/f; P700; Photosynthesis

Journal Article.  0 words. 

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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