Mechanism of Heat Induced Stimulation of PSI Activity in Pea Chloroplasts

  • Maya Velitchkova
  • Alexander G. Ivanov
  • Rosa Petkova
Part of the NATO ASI Series book series (NSSA, volume 168)


It was well documented1,2 that short time heat stress (5 min at 50o) results in an increase of PSI-mediated electron transport rate. An explanation of this phenomenon has been given by Thomas et al.2, who proposed an exposure of new electron donor sites within cyt b6/f complex for the artificial electron donor. Considerable increase (50%) of light-induced ESRI signal (P700+) in heat stressed chloroplasts was also reported3. Recently, it was demonstrated4, that even at very low light intensity the amplitude of P700+ remains higher and that under limiting light conditions P700 photo-oxidation occurs faster in heat-treated chloroplasts. It was supposed3,4, that the mechanism of heat-induced stimulation of P700 photoconversion includes a redistribution of the excitation light energy in favor to PSI via an increase of PSI absorption cross section and enhancement of the spillover. This assumption was made on the basis of the well established heat-indu*-ced structural reorganization of the thylakoid membranes — randomization of the pigment-protein complexes of PSII and PSI, dissociation of LHCa/b protein complex from core complex of PSII and its possible lateral migration along the thylakoid membrane to the PSI-enriched stroma lamellae. In the present study the effects of heat-stress on the energy distribution and PSI electron transport rate in total thylakoids and stromal thylakoid fractions were compared.


Chlorophyll Fluorescence Thylakoid Membrane Fluorescence Rise Stromal Thylakoid Stromal Fraction 
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  1. 1.
    M. A. Stidham, E. G. Uribe and G. J. Williams III, Temperature depen-dence of photosynthesis in Agropyron smithii Ridb. II Contribution from electron transport and photophosphorylation, Plant Physiol. 69:929 (1982).PubMedCrossRefGoogle Scholar
  2. 2.
    P. G. Thomas, P. J. Quinn and W. P. Williams, The origin of photosystem-I-mediated electron transport stimulation in heat-stressed chloroplasts, Planta 167:133 (1986).CrossRefGoogle Scholar
  3. 3.
    A. G. Ivanov, M. Y. Velitchkova and D. N. Kafalieva, Heat-induced changesin photosystem I reaction centre in pea chloroplast membranes, Compt. rend. Acad. bulg. Sci, 39:123 (1986).Google Scholar
  4. 4.
    M. Velitchkova and A. Ivanov, Light intensity dependence of P700 photooxidation in heat stressed pea chloroplasts, in: “Electromagnetic Fields and Biomembranes”, M. Markov and M. Blank, eds., Plenum Press, New York and London.(1988).Google Scholar
  5. 5.
    K. Gounaris, A. P. R. Brain, P. J. Quinn and W. P. Williams, Structural reorganization of chloroplast thylakoid membranes in response to heat-stress, Biochim. Biophys. Acta 766:198 (1984).CrossRefGoogle Scholar
  6. 6.
    C. Sundby and B. Andersson, Temperature-induced reversible migration along the thylakoid membrane of photosystem II regulates its association with LHC-II, FEBS Lett. 191:24 (1985).CrossRefGoogle Scholar
  7. 7.
    R. C. Ford, D. J. Chapman. J. Barber, J. Z. Pedersen and R. D. Cox, Fluorescence polarization and spin-label studies of the fluidity of the stromal and granal chloroplast membranes, Biochim. Biophys. Acta 681:145 (1982).CrossRefGoogle Scholar
  8. 8.
    A. R. Wellburn and H. Lichtenthaler, Formulae and program to determine total carotenoids and chlorophyll a and b . Leaf extracts in different solvents, Adv. Photosynth. Res.2:9 (1984).Google Scholar
  9. 9.
    U. Schreiber and P. A. Armond, Heat-induced changes of chlorophyll fluorescence in isolated chloroplasts and related heat-damage at the pigment level, Biochim. Biophys. Acta 502:138 (1978).PubMedCrossRefGoogle Scholar
  10. 10.
    D. R. Allred and L. A. Staehelin, Implications for cytochrome b6/f location for thylakoid electron transport, J. Bioenerg. Biomembr.18: 419 (1986).PubMedCrossRefGoogle Scholar

Copyright information

© Plenum Press, New York 1989

Authors and Affiliations

  • Maya Velitchkova
    • 1
  • Alexander G. Ivanov
    • 1
  • Rosa Petkova
    • 2
  1. 1.Bulgarian Academy of SciencesCentral Laboratory of BiophysicsSofiaBulgaria
  2. 2.Institute of Plant PhysiologySofiaBulgaria

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