Kinetics of the dichroic reorientation of phytochrome during photoconversion inMougeotia |
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Authors: | Manfred Kraml Margit Enders Nobert Bürkel |
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Affiliation: | (1) Botanisches Institut der Universität, Schlossgarten 4, D-8520 Erlangen, Federal Republic of Germany |
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Abstract: | In the green algaMougeotia, the dichroic orientation of the red-absorbing form of phytochrome (Pr) is parallel of the cell surface, whereas the far-red-absorbing form (Pfr) is oriented normal to it. The time course of the change from parallel to normal was investigated by double-flash irradiation with polarized red and far-red light. The results obtained by two different methods indicate that most of the phytochrome intermediates existing in the first 5 ms after the inducing red flash are still oriented parallel to the cell surface, similar to Pr. At increasing intervals between the red and the far-red flashes, more and more phytochrome molecules turn their transition moments to the Pfr orientation. This reaction is finished after approximately 30 ms. We conclude that the change in dichroic orientation of the phytochrome molecules inMougeotia occurs during the last relaxation steps of the intermediates on the way from Pr to Pfr. It cannot be decided yet, whether the first surface-normal phytochrome species is an intermediate or Pfr itself.Abbreviations Pr red-absorbing form of phytochrome - Pfr far-red-absorbing form of phytochromeA preliminary report of this work was presented at the European Symposium on Photomorphogenesis, University of Reading, UK (Kraml et al. 1982) |
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Keywords: | Chloroplast movement Dichroic reorientation Mougeotia Photoconversion kinetics Phytochrome intermediate |
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