Membrane lipid peroxidation, cell viability and Photosystem II activity in the green alga Chlorella pyrenoidosa subjected to various stress conditions
✍ Scribed by Dmitrii V. Vavilin; Jean-Marc Ducruet; Dmitrii N. Matorin; Pavel S. Venediktov; Andrey B. Rubin
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 603 KB
- Volume
- 42
- Category
- Article
- ISSN
- 1011-1344
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✦ Synopsis
The unicellular green alga Chlorella pyrem~idosa was subjected to a variety of stress conditions ( strong illumination, incubation with Cu 2 or Zn 2+ , exposure to high temperatures). The amplitude of thermoluminescence (TL) peak at 125°C. accunmlation of thiobarbituric acid reactive substances (TBARS), which indicate an accumulation of lipid peroxidation products, efficiency of Photosystem 11 reactions { Fv/ F,a ratio) and the percentage of viable cells were measured in stressed culture. Exposure of algae to strong (5001) ixmol photons m : s ~ ) or to low ( 6(1 ~mol photons m : s t ) light combined with the addition of 1.6 0,M Cu 2 ' or 30 ixM Zn-' + inactivated Photosystem lI, decreased the viability of Chlorella cells, and, finally, significantly enhanced TL and the accumulation of TBARS, which was accompanied by chlorophyll bleaching. TL emission started to rise after a lag-period of about 30 rain in algae subjected to strong illumination, 2-3 h in copper-treated algae, and 10 h in zinc-treated algae. A vast majority of cells were nonviable to the end of the lag-period. The addition of Cu -~ ' or Zn -~ ~ in darkness caused a slight decrease in the F v/FM ratio without significant changes in TL emission. Incubation of algae at 50°C for I1) rain did not affect the Fv/FM ratio and cell viability, whereas no viable cells and Photosystem II activity were detected in the culture incubated at 55°C. Heat stress at temperatures above 55°C significantly enhanced the amplitude of the 125°C TL peak and the accumulation of TBARS when the algae were further incubated at low light at room temperature. We conclude that, under the stress conditions used in this study. ( i ) lipid peroxides and products ,,ff their degradation are not responsible for the cytolethal effect in Chlorella and ( iii lipid peroxidation arises mainly upon illumination of dead cells.