Atrazine and Methyl Viologen Effects on Chlorophyll‐a Fluorescence Revisited—Implications in Photosystems Emission and Ecotoxicity Assessment

Abstract

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 reabsorption processes, allowed us to elucidate current controversies in the subject. Results were compatible with the fact that a nonnegligible Photosystem I contribution to chlorophyll fluorescence in plants at room temperature does exist. In another aspect, variable and nonvariable 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 to 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.

Melatonin Application to Pisum sativum L. Seeds Positively Influences the Function of the Photosynthetic Apparatus in Growing Seedlings during Paraquat-Induced Oxidative Stress

“…Due to potent action of PQ for blocking the photosynthesis process, its influence on the chlorophyll fluorescence parameters has been widely investigated; these parameters are highly sensitive indicators of stress intensity (Guo et al, 2007; Rodriguez et al, 2012; Iriel et al, 2014; Moustaka and Moustakas, 2014; Moustaka et al, 2015). Herein, we performed PAM analyses after leaves were incubated for 2, 4, or 6 h with PQ.…”

“…In plants the energy absorbed by chlorophyll a is utilized/deactivated in three different means: (a) a major portion is used for non-cyclic (ATP and NADPH synthesis) or cyclic (ATP synthesis) electron transfer in photosynthesis, (b) excess energy is dissipated as heat, (c) energy is emitted as light (fluorescence; Iriel et al, 2014). Measuring chlorophyll fluorescence is a great tool in determining the photosynthetic efficiency.…”

Photochemical changes and oxidative damage in the aquatic macrophyte Cymodocea nodosa exposed to paraquat-induced oxidative stress

“…The conclusion that Φ PSII was a more sensitive indicator of herbicide impact than F v /F m has been also reported by many researchers [10,11]. Recently the effective quantum yield of PSII photochemistry (Φ PSII ) was proposed as the most sensitive bioindicator for both Pq and atrazine [14]. Frankart et al [1] proposed the use of non-photochemical quenching (NPQ) as a biomarker in laboratory and field herbicide bioassays.…”

“…Although Φ PSII was adopted as the most sensitive bioindicator to evaluate toxic effect of herbicides by many researchers [10][11][12]14], we believe that the use of NPQ that was proposed by Frankart et al [1], Juneau et al [10] and by Moustaka and Moustakas [3], together with Φ NO and the fraction of open PSII reaction centers (q p ), must be taken into account in order to evaluate herbicide's action on PSII photochemistry.…”

Effects of controlled oxidative stress and uncouplers on primary photosynthetic processes in vegetative cells of Antarctic alga Zygnema sp.

“…Therefore, MV suppresses cyclic electron transfer around PS I (Cornic et al 2000). In fluorometric studies of higher plants devoted to functioning of their photochemical photosynthetic processes, MV effects on OJIPs (Schansker et al 2005) and slow chlorophyll kinetics (Iriel et al 2014) were studied. Recent studies (e.g.…”