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- Title
THE EFFECT OF DIFFERENT LIGHT INTENSITIES ON PHOTOCHEMICAL ACTIVITY IN MICROCYSTIS AERUGINOSA AICB 702 STRAIN (CYANOPHYTA).
- Authors
HEGEDŰS, ADRIANA; BERCEA, VICTOR; DRUGĂ, BOGDAN; SICORA, COSMIN
- Abstract
Microcystis aeruginosa AICB 702 was grown at room temperature, on GZ medium, in air-lift conditions, using a medium light intensity of 260 μmol. m-2.s-1. The exponential-phase cells were exposed to 800, 1500 and 2100 μmol. m-2.s-1 light intensities and the fluorescence measurements were performed after 15, 30, 45, 60, 75, 90, 105 and 120 minutes of light exposure. Dark-adapted probes were analyzed after 120 minutes recovery period. The oxidation state of primary acceptor and the fraction of the reaction centers are reduced (damaged), the photochemical process and the light harvesting are slightly inhibited when an 800 μmol. m-2.s-1 light intensity is used. Also, the reduction of the primary acceptor and the reaction centers closure were maximal. The Fv/Fm and Y(II) quantum yield were inhibited. The Fv/Fm values registered toward the end of the experiment represented 46.5% of the theoretical value, which also indicates the ratio of the PS II reaction centers that were photoinhibited. The nonregulated energy dissipation increased, and the high values of qP and qL coefficients showed an enhanced photochemical process with a low fluorescence emission. Increased F0 and Fm and Fv decreased when 1500 μmol.m-2.s-1 was used. The Fv/Fm and Y(II) diminished and the non-regulated energy dissipation increased. When a light intensity of 2100 μmol.m-2.s-1was used, the Fo raised during a 90 min period, then decreased to 85%. Fm and Fv decreased, also. The Fv/Fm and Y(II) diminished, while the non-regulated energy dissipation increased. The decrease of F0, Fm and Fv/Fm yield and that of the Y(II) certified the photoinhibition effect of 2100 μmol.m-2.s-1 light intensity on the activities carried out by the photosystems antenna. When an 800 μmol.m-2.s-1 light intensity was used the recovery of the photosynthetic activity was faster compared with other high-light intensities treatments.
- Subjects
MICROCYSTIS aeruginosa; CYANOBACTERIA; LIGHT intensity; PHOTOSYNTHETIC reaction centers; ENERGY dissipation; PLANT photoinhibition
- Publication
Studia Universitatis Babeş-Bolyai, Biologia, 2013, Vol 58, Issue 1, p71
- ISSN
1221-8103
- Publication type
Article