Photosynthesis Research

, Volume 40, Issue 1, pp 35–44

Pigment orientation changes accompanying the light state transition in Synechococcus sp. PCC 6301

  • Jill A. Homer-Dixon
  • Elisabeth Gantt
  • Doug Bruce
Regular Paper

DOI: 10.1007/BF00019043

Cite this article as:
Homer-Dixon, J.A., Gantt, E. & Bruce, D. Photosynth Res (1994) 40: 35. doi:10.1007/BF00019043


Low temperature (77 K) linear dichroism spectroscopy was used to characterize pigment orientation changes accompanying the light state transition in the cyanobacterium, Synechococcus sp. PCC 6301 and those accompanying chromatic acclimation in Porphyridium cruentum in samples stabilized by glutaraldehyde fixation. In light state 2 compared to light state 1 intact cells of Synechococcus showed an increased alignment of allophycocyanin parallel to the cells' long axis whereas the phycobilisomethylakoid membrane fragments exhibited an increased allophycocyanin alignment parallel to the membrane plane. The phycobilisome-thylakoid membrane fragments showed less alignment of a short wave-length chlorophyll a (Chl a) Qy transition dipole parallel to the membrane plane in state 2 relative to state 1.

To aid identification of the observed Chl a orientation changes in Synechococcus, linear dichroism spectra were obtained from phycobilisome-thylakoid membrane fragments isolated from red light-grown (increased number of PS II centres) and green light-grown (increased number of PS I centres) cells of the red alga Porphyridium cruentum. An increased contribution of short wavelength Chl a Qy transition dipoles parallel to the long axis of the membrane plane was directly correlated with increased levels of PS II centres in red light-grown P. cruentum.

Our results indicate that the transition to state 2 in cyanobacteria is accompanied by an increase in the orientation of allophycocyanin and a decrease in the orientation of Chl a associated with PS II with respect to the thylakoid membrane plane.

Key words

allophycocyanin chlorophyll a linear dichroism phycobilisome photosynthesis state transition 




Chl a -

chlorophyll a



LD -

linear dichroism

LD/A -

linear dichroism divided by absorbance


light-harvesting complex



PC -


PS -



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Copyright information

© Kluwer Academic Publishers 1994

Authors and Affiliations

  • Jill A. Homer-Dixon
    • 1
  • Elisabeth Gantt
    • 2
  • Doug Bruce
    • 1
  1. 1.Department of Biological SciencesBrock UniversitySt. CatharinesCanada
  2. 2.Department of Botany and Maryland Agricultural Experiment StationUniversity of MarylandCollege ParkUSA

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