Comparative effects of four herbicides on non-photochemical fluorescence quenching in Lemna minor

摘要: Abstract Aquatic ecosystems are exposed to an increasing contamination of pesticides such as herbicides through water runoff. The pulse-amplitude-modulation (PAM) fluorometric method, a sensitive and rapid was used evaluate toxic effect these pollutants in Lemna minor . Four (paraquat, norflurazon, flazasulfuron atrazine) often found outdoor samples inducing specific changes the yield vivo chlorophyll fluorescence PSII were selected. These affected photosynthesis via different ways by: accepting electron from PSI, inhibiting carotenoids protein biosynthesis or blocking transport. Data revealed that photosynthetic parameters based on emission modified with increase herbicide concentration. toxicity compounds follows (from greatest least): paraquat>norflurazon>atrazine>flazasulfuron. Growth rate pigments analysis confirmed results obtained PAM fluorometry. We among non-photochemical quenching most appropriate indicator for effects herbicides. components then resolved by examination relaxation kinetics upon DCMU addition light saturation pulse entire plant. Three kinetically distinct phases observed which have previously been identified thylakoids ( Horton Hague, 1988 ) being due energy-state (qE), state transition (qT) photoinhibition (qI). examined NPQ showed levels sensitivity herbicide. It that: (i) qE major component; (ii) all selected herbicides; (iii) qT significantly paraquat atrazine; (iv) qI norflurazon flazasulfuron. interpreted pesticide mode-of-action. This study shows use biomarker may be laboratory field bioassays. Moreover, application allow better understanding mechanism action.