Atrazine and Methyl viologen effects on Chlorophyll-a fluorescence revisited. Implications in Photosystems Emission and Ecotoxicity Assessment

ANALÍA IRIEL; JOHANNA MENDES NOVO; GABRIELA B. CORDON ; MARIA GABRIELA LAGORIO

PHOTOCHEMISTRY AND PHOTOBIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: New York; Año: 2014 p. 107 - 112

0031-8655

In this work we use the effect of herbicides that affect the photosynthetic chain at defined sites in the photosynthetic reaction steps to derive information about the fluorescence emission of photosystems. The interpretation of spectral data from treated and control plants, after correction for light re-absorption processes, allowed us to elucidate current controversies in the subject. Results were compatible with the fact that a non-negligible Photosystem I contribution to chlorophyll fluorescence in plants at room temperature does exist. In another aspect, variable and non-variable chlorophyll fluorescence were comparatively tested as bioindicators for detection of both herbicides in aquatic environment. Both methodologies were appropriate tools for this purpose. However, they showed better sensitivity for pollutants disconnecting Photosystem II-Photosystem I by blocking the electron transport between them as Atrazine. Specifically, changes in the (experimental and corrected by light reabsorption) red-far red fluorescence ratio, in the maximum photochemical quantum yield and in the quantum efficiency of Photosytem II for increasing concentrations of herbicides have been measured and compared. The most sensitive bioindicator for both herbicides was the quantum efficiency of Photosystem II.