Chlorophyll Fluorescence as a rapid assay method for ecotoxicity assessment

MENDES NOVO, J.; CORDON, G.; IRIEL, A.; LAGORIO, M. G.

Proceedings of the International Congress of Environmental Science and Technology

Asociación Argentina para el Progreso de las Ciencias

Lugar: Buenos Aires; Año: 2012; p. 769 - 774

Chlorophyll emission from intact plant leaves is related to the physiological state of photosystems I and II (PSI and II) and to its photosynthetic activity. Stress conditions disturbing either the electron transport in the chloroplasts or the pigments and protein degradation are expected to lead to changes in chlorophyll emission. According to the measuring conditions, two kinds of experiments are possible: i) recording the spectral distribution of the initial non-variable fluorescence (F0) under a photon flow low enough to avoid photosynthesis and ii) recording a variable fluorescence as a function of time upon photosynthesis induction. The first experiment gives information on the photosystems stoichiometry while the second one allows determination of several photosynthetic parameters. The objective of the present research was to explore the applicability of non-destructive fluorescence measurements in ecotoxicity evaluation. In this work we have studied changes in chlorophyll emission after the action of two herbicides: Atrazine (affecting the electron transport) and Methyl viologen (producing reactive oxygen species and protein degradation). The study was performed on the species Ficus benjamina, Hedera helix and Spathiphyllum wallisi. Both, the steady state and the time-resolved experiments were performed. From F0 measurements, the fluorescence ratio between maxima in the red and far-red were obtained. They were also corrected by light re-absorption processes. Atrazine presence led to higher fluorescence ratios while Methyl viologen led to lower values compared to controls, in all the cases. From variable measurements, the maximum quantum efficiency of PSII photochemistry (Fv/Fm) and the quantum efficiency of PSII (FPSII) were determined in both cases. The most sensitive parameter responding to the stress situations resulted to be FPSII.   References -Lagorio, M. G., 2011. Chlorophyll fluorescence emission spectra in photosynthetic organisms in Chlorophyll: Structure, Production and Medicinal Uses. Nova Sci. Pub., NY. -Cordon, G. B. and Lagorio M. G., 2006. Re-absorption of chlorophyll fluorescence in leaves revisited. A comparison of correction models. Photochem. Photobiol. Sci., 5, 735-740. Acknowledgement: University of Buenos Aires (Projects UBACyT X114 and UBACyT 20020100100814). Agencia Nacional de Promoción Científica y Tecnológica (BID 1201/OC-AR PICT 938). CONICET fellowship (GBC) and UBA fellowship (JMN) Keywords: Chlorophyll fluorescence, Photosynthesis, Herbicides, Toxicity, Bioassay