Planta

, Volume 188, Issue 3, pp 422–431

Mechanistic differences in photoinhibition of sun and shade plants

  • Gunnar Öquist
  • Jan M. Anderson
  • Stephanie McCaffery
  • W. S. Chow
Article

DOI: 10.1007/BF00192810

Cite this article as:
Öquist, G., Anderson, J.M., McCaffery, S. et al. Planta (1992) 188: 422. doi:10.1007/BF00192810

Abstract

Leaf discs of the shade plant Tradescantia albiflora Kunth grown at 50 μmol · m−2 · s−1, and the facultative sun/shade plant Pisum sativum L. grown at 50 or 300 μmol · m−2, s−1, were photoinhibited for 4 h in 1700 μmol photons m−2 · s−1 at 22° C. The effects of photoinhibition on the following parameters were studied: i) photosystem II (PSII) function; ii) amount of D1 protein in the PSII reaction centre; iii) dependence of photoinhibition and its recovery on chloroplast-encoded protein synthesis; and, iv) the sensitivity of photosynthesis to photoinhibition in the presence or absence of the carotenoid zeaxanthin. We show that: i) despite different sensitivities to photoinhibition, photoinhibition in all three plants occurred at the reaction centre of PSII; ii) there was no correlation between the extent of photoinhibition and the degradation of the D1 protein; iii) the susceptibility to photoinhibition by blockage of chloroplas-tencoded protein synthesis was much less in shade plants than in plants acclimated to higher light; and iv) inhibition of zeaxanthin formation increased the sensitivity to photoinhibition in pea, but not in the shade plant Tradescantia. We suggest that there are mechanistic differences in photoinhibition of sun and shade plants. In sun plants, an active repair cycle of PSII replaces photoinhibited reaction centres with photochemically active ones, thereby conferring partial protection against photoinhibition. However, in shade plants, this repair cycle is less important for protection against photoinhibition; instead, photoinhibited PSII reaction centres may confer, as they accumulate, increased protection of the remaining connected, functional PSII centres by controlled, nonphotochemical dissipation of excess excitation energy.

Key words

Light acclimationPhotosynthesisPhotoinhibitionPhotosystem II repair cyclePisumTradescantia

Abbreviations and Symbols

CAP

chloramphenicol

DTT

dithiothreitol

Fv/Fm

the ratio of variable to maximal fluorescence as an expression of the maximal quantum yield of photochemistry in PSII in dark-acclimated leaves

F′v and F′m

denote variable and maximal fluorescence under steady-state light conditions

F′v/F′m

the quantum yield of photochemistry in PSII during steady-state illumination

PSII

photosystem II

qp

photochemical quenching of fluorescence

øe

quantum yield of PSII electron transport during steady illumination

Copyright information

© Springer-Verlag 1992

Authors and Affiliations

  • Gunnar Öquist
    • 1
  • Jan M. Anderson
    • 1
  • Stephanie McCaffery
    • 1
  • W. S. Chow
    • 1
  1. 1.Division of Plant IndustryCSIROCanberraAustralia
  2. 2.Department of Plant PhysiologyUniversity of UmeåUmeåSweden