Journal Article

Role of light in the response of PSII photochemistry to salt stress in the cyanobacterium <i>Spirulina platensis</i>

Congming Lu and Jianhua Zhang

in Journal of Experimental Botany

Volume 51, issue 346, pages 911-917
Published in print May 2000 | ISSN: 0022-0957
Published online May 2000 | e-ISSN: 1460-2431 | DOI: http://dx.doi.org/10.1093/jexbot/51.346.911
Role of light in the response of PSII photochemistry to salt stress in the cyanobacterium Spirulina platensis

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The role of light in the effect of salt stress on PSII photochemistry in the cyanobacterium Spirulina platensis grown at 50 μmol m−2 s−1 was investigated. The time‐course of changes in PSII photochemistry in response to high salinity (0.8 M NaCl) incubated in the dark and at 30, 50 and 100 μmol m−2 s−1 was composed of two phases. The first phase, which was independent of light, was characterized by a rapid decrease (20–50%) in the maximal efficiency of PSII photochemistry (Fv/Fm), the efficiency of excitation energy capture by open PSII reaction centres ([math]/[math]), photochemical quenching (qP), and the quantum yield of PSII electron transport (ΦPSII) in the first 15 min, followed by a recovery of up to about 86–92% of their initial levels after 4 h of incubation. The second phase took place after 4 h, in which a further decline in the above parameters occurred only in the light but not in the dark, reaching levels as low as 32–56% of their initial levels after 12 h. Moreover, the higher incubation light intensity, the greater the decrease in the above parameters. At the same time, QB‐non‐reducing PSII reaction centres increased significantly in the first 15 min and then recovered to the initial level during the first phase, but increased again in the light in the second phase. Photosynthetic oxygen evolution activity decreased sharply by 70% in the first 5 min, and then kept largely constant until 12 h. The changes in oxygen evolution activity were independent of light intensity during both phases.

Keywords: Chlorophyll fluorescence; light effect; PSII photochemistry; salt stress; Spirulina platensis; cyanobacterium.; Fo, minimal fluorescence level in the dark‐adapted state; \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathit{F}_{o}^{{^\prime}}\) \end{document}, minimal fluorescence level in light‐adapted state; Fm, maximal fluorescence level in dark‐adapted state; \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathit{F}_{m}^{{^\prime}}\) \end{document}, maximal fluorescence level in light‐adapted state; Fv, maximum variable fluorescence level in the dark‐adapted state; \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathit{F}_{v}^{{^\prime}}\) \end{document}, maximum variable fluorescence level in the light‐adapted state; Fs, steady‐state fluorescence level at qP>0; Fv/Fm, maximal efficiency of PSII photochemistry; ΦPSII, quantum yield of PSII electron transport; \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathit{F}_{v}^{{^\prime}}\) \end{document}/\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathit{F}_{m}^{{^\prime}}\) \end{document}, efficiency of excitation energy capture by open PSII reaction centres; QA, primary quinone electron acceptor of PSII; QB, secondary quinone electron acceptor of PSII; qP, photochemical quenching coefficient.

Journal Article.  4902 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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