Journal
BIOLOGICAL TRACE ELEMENT RESEARCH
Volume 160, Issue 2, Pages 268-275Publisher
HUMANA PRESS INC
DOI: 10.1007/s12011-014-0039-z
Keywords
Copper; Cyclic electron flow; Dual-PAM-100; Electron transport; Photosystem I
Funding
- National Natural Science Foundation of China [U1120302, 21177127]
- Specialized Research Fund for the Doctoral Program of Higher Education [20125303120003]
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Responses of photosystem I and II activities of Microcystis aeruginosa to various concentrations of Cu2+ were simultaneously examined using a Dual-PAM-100 fluorometer. Cell growth and contents of chlorophyll a were significantly inhibited by Cu2+. Photosystem II activity [Y(II)] and electron transport [rETR(max)(II)] were significantly altered by Cu2+. The quantum yield of photosystem II [Y(II)] decreased by 29 % at 100 mu g L-1 Cu2+ compared to control. On the contrary, photosystem I was stable under Cu2+ stress and showed an obvious increase of quantum yield [Y(I)] and electron transport [rETR(max)(I)] due to activation of cyclic electron flow (CEF). Yield of cyclic electron flow [Y(CEF)] was enhanced by 17 % at 100 mu g L-1 Cu2+ compared to control. The contribution of linear electron flow to photosystem I [Y(II)/Y(I)] decreased with increasing Cu2+ concentration. Yield of cyclic electron flow [Y(CEF)] was negatively correlated with the maximal photosystem II photochemical efficiency (F (v)/F (m)). In summary, photosystem II was the major target sites of toxicity of Cu2+, while photosystem I activity was enhanced under Cu2+ stress.
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