Evidence for the role of the light-harvesting chlorophyll a b protein complex in photosystem II heterogeneity

Michael P. Percival, Andrew N. Webber, Neil R. Baker

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

Analyses of chlorophyll fluorescence induction kinetics from DCMU-poisoned thylakoids were used to examine the contribution of the light-harvesting chlorophyll a b protein complex (LHCP) to Photosystem II (PS II) heterogeneity. Thylakoids excited with 450 nm radiation exhibited fluorescence induction kinetics characteristic of major contributions from both PS IIα and PS IIβ centres. On excitation at 550 nm the major contribution was from PS IIβ centres, that from PS IIα centres was only minimal. Mg2+ depletion had negligible effect on the induction kinetics of thylakoids excited with 550 nm radiation, however, as expected, with 450 nm excitation a loss of the PS IIα component was observed. Thylakoids from a chlorophyll-b-less barley mutant exhibited similar induction kinetics with 450 and 550 nm excitation, which were characteristic of PS IIβ centres being the major contributors; the PS IIα contribution was minimal. The fluorescence induction kinetics of wheat thylakoids at two different developmental stages, which exhibited different amounts of thylakoid appression but similar chlorophyll a b ratios and thus similar PS II:LHCP ratios, showed no appreciable differences in the relative contributions of PS IIα and PS IIβ centres. Mg2+ depletion had similar effects on the two thylakoid preparations. These data lead to the conclusion that it is the PS II:LHCP ratio, and probably not thylakoid appression, that is the major determinant of the relative contributions of PS IIα and PS IIβ to the fluorescence induction kinetics. PS IIα characteristics are produced by LHCP association with PS II, whereas PS IIβ characteristic can be generated by either disconnecting LHCP from PS II or by preferentially exciting PS II relative to LHCP.

Original languageEnglish (US)
Pages (from-to)582-589
Number of pages8
JournalBBA - Bioenergetics
Volume767
Issue number3
DOIs
StatePublished - Dec 18 1984
Externally publishedYes

Keywords

  • (Wheat, Barley, Chloroplast)
  • Chlorophyll fluorescence
  • Chlorophyll-protein complex
  • Fluorescence induction kinetics
  • Light-harvesting complex
  • Photosystem II

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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