Photoinhibition of Reaction Centre Activity in Photosystem Two Preparations with Reduced Rates of Water Oxidation
Significant reduction in photosynthetic rate and subsequent loss of crop yield can occur as a result of increases in light intensity in field environments, particularly when there is an additional stress factor such as that of low temperature (Powles, 1984). Although attempts to understand the molecular basis of this photoinhibition have been largely unsuccessful, it has been clearly shown that the primary sites of damage are the photosystems which drive the electron transfer reactions of photosynthesis (Kyle, 1987). Inactivation of the photosystems arises largely because the many pigment molecules in the leaf absorb and then transfer light energy to the reaction centre of the photosytems and this focus of energy gives the potential for initiation of damaging reactions. Damage is likely to occur if dissipation of energy is not achieved by the maintenance of sufficiently high rates of electron flow and it has been suggested that factors which enhance photoinhibition, such as low CO2 levels, could act through reducing rates of electron transfer (Powles, 1984). In this context there are many points at which electron flow could be inhibited although the main locus for photodamage seems to be photosystem two (PS2) (Kyle, 1987). Here we report our work on the significance of impaired water oxidation and electron donation to the PS2 reaction centre.
KeywordsWater Oxidation Dark Control Extrinsic Protein Photosynthetic Oxygen Evolution Reaction Centre Activity
Unable to display preview. Download preview PDF.
- Chapman, D.J., De Felice, J., Davis, K. and Barber, J. Effect of alkaline pH on photosynthetic water oxidation and the association of extrinsic proteins with photosystem two. Biochem. J. 258 in press (1989)Google Scholar
- Kyle, D.J. The biochemical basis for photoinhibition of photosystem II. In: Topics in Photosynthesis Vol.9. Photoinhibition ed. Kyle, D.J., Osmond, B. and Arntzen, C.J., Pub. Elsevier Science Publishers, B.V., Amsterdam pp 197–226 (1987)Google Scholar
- Kuwabara, T. and Murata, N. Inactivation of photosynthetic oxygen evolution and concomitant release of three polypeptides in the photosystem II particles of spinach chloroplasts. Plant & Cell Physiol. 23;533–539 (1982)Google Scholar
- Powles, S.B. Photoinhibition of photosynthesis induced by visible light. Annu. Rev. Plant Physiol. 35; 15–44Google Scholar
- Theg, S.M., Filar, L.J. and Dilley, R.A. Photoinactivation of chloroplasts already inhibited on the oxidising side of photosystem II. Biochim. Biophys. Acta 849;104–111Google Scholar