title: Differential effects of glyphosate and aminomethylphosphonic acid (AMPA) on photosynthesis and chlorophyll metabolism in willow plants.
abstract: We used a willow species (Salix miyabeana cultivar SX64) to examine the differential secondary-effects of glyphosate and aminomethylphosphonic acid (AMPA), the principal glyphosate by-product, on chlorophyll metabolism and photosynthesis. Willow plants were treated with different concentrations of glyphosate (equivalent to 0, 1.4, 2.1 and 2.8kgha(-1)) and AMPA (equivalent to 0, 0.28, 1.4 and 2.8kgha(-1)) and evaluations of pigment contents, chlorophyll fluorescence, and oxidative stress markers (hydrogen peroxide content and antioxidant enzyme activities) in leaves were performed after 12h of exposure. We observed that AMPA and glyphosate trigger different mechanisms leading to decreases in chlorophyll content and photosynthesis rates in willow plants. Both chemicals induced ROS accumulation in willow leaves although only glyphosate-induced oxidative damage through lipid peroxidation. By disturbing chlorophyll biosynthesis, AMPA induced decreases in chlorophyll contents, with consequent effects on photosynthesis. With glyphosate, ROS increases were higher than the ROS-sensitive threshold, provoking chlorophyll degradation (as seen by pheophytin accumulation) and invariable decreases in photosynthesis. Peroxide accumulation in both AMPA and glyphosate-treated plants was due to the inhibition of antioxidant enzyme activities. The different effects of glyphosate on chlorophyll contents and photosynthesis as described in the literature may be due to various glyphosate:AMPA ratios in those plants.
authors.affiliation: Université du Québec à Montréal, Department of Biological Sciences, TOXEN, Ecotoxicology of Aquatic Microorganisms Laboratory, Succ. Centre-Ville, Montréal H3C 3P8, Québec, Canada; Université du Québec à Montréal, Institut des Sciences de l'environnement & GEOTOP, Succ. Centre-Ville, C.P. 8888, Montréal H3C 3P8, Québec, Canada.
authors.forename: Marcelo Pedrosa
authors.initials: MP
authors.lastname: Gomes
authors.affiliation: Université du Québec à Montréal, Department of Biological Sciences, TOXEN, Ecotoxicology of Aquatic Microorganisms Laboratory, Succ. Centre-Ville, Montréal H3C 3P8, Québec, Canada.
authors.forename: Sarah Gingras
authors.initials: SG
authors.lastname: Le Manac'h
authors.affiliation: Université du Québec à Montréal, Institut des Sciences de l'environnement & GEOTOP, Succ. Centre-Ville, C.P. 8888, Montréal H3C 3P8, Québec, Canada.
authors.forename: Sophie
authors.initials: S
authors.lastname: Maccario
authors.affiliation: Institut de Recherche en Biologie Végétale, Montreal Botanical Garden, 4101 Sherbrooke East, Montréal H1X 2B2, Québec, Canada.
authors.forename: Michel
authors.initials: M
authors.lastname: Labrecque
authors.affiliation: Université du Québec à Montréal, Institut des Sciences de l'environnement & GEOTOP, Succ. Centre-Ville, C.P. 8888, Montréal H3C 3P8, Québec, Canada.
authors.forename: Marc
authors.initials: M
authors.lastname: Lucotte
authors.affiliation: Université du Québec à Montréal, Department of Biological Sciences, TOXEN, Ecotoxicology of Aquatic Microorganisms Laboratory, Succ. Centre-Ville, Montréal H3C 3P8, Québec, Canada. Electronic address: juneau.philippe@uqam.ca.
authors.forename: Philippe
authors.initials: P
authors.lastname: Juneau
mesh_terms: D002734:Chlorophyll / Q000378:metabolism*; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006540:Herbicides / Q000494:pharmacology*; D007555:Isoxazoles; D063065:Organophosphonates / Q000494:pharmacology*; D010084:Oxidation-Reduction / Q000187:drug effects; D010788:Photosynthesis / Q000187:drug effects*; D032108:Salix / Q000187:drug effects* / Q000378:metabolism; D013777:Tetrazoles; D000097797:Glyphosate
chemical_list: D002734:Chlorophyll; D005998:Glycine; D006540:Herbicides; D007555:Isoxazoles; D063065:Organophosphonates; D013777:Tetrazoles; D000097797:Glyphosate; C418233:2-amino-3-(3-hydrox-5(2-methyl-2H-tetrazol-5-yl)isoxazol-4-yl)propionic acid
keywords: Aminolevulinic acid; Herbicide; Oxidative stress; Photosynthesis; Pigments; ROS