Authors: Benoît Schoefs Fabrice Franck
Publish Date: 2007/11/03
Volume: 96, Issue: 1, Pages: 15-26
Abstract
The photoenzymatic cycle of the lightdependent NADPHprotochlorophyllide oxidoreductase LPOR was investigated in situ during early stages of development of bean leaves under lightdark cycles LDC In the experimental system used in this study prolamellar bodies developed during night periods and disappeared during light periods This was accompanied by changes in the photoactive to nonphotoactive Pchlide ratio which was higher at the end of the light period and tended to increase with the number of LDC’s Flashinduced absorbance changes in the Chlide absorption region 700 nm were used in order to monitor the formation of short and longwavelength forms of Chlide C670–675 and C682–694 which correspond to free Chlide and aggregated ChlideNADPHLPOR complexes respectively The ratio of longwavelength to shortwavelength Chlides after one flash increased with the number of LDC’s and was higher in leaves collected at the end of light periods compared to leaves collected at the end of night periods During light periods photoactive Pchlide regeneration and Chlide phytylation were completed within 1 min after flashinduced formation of longwavelength Chlide The results show for the first time that the photoenzymatic LPOR cycle proceeds through similar steps but at much faster rates during photoperiodic greening than in the previously studied leaves of etiolated plants In particular the parallel formation of two Chlide species always occurs but the ratio of the two species depends on the ratio of photoactive to nonphotoactive Pchlide and on light or dark adaptation
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