title: Glyphosate-Dependent Inhibition of Photosynthesis in Willow.
abstract: We studied the physiological mechanisms involved in the deleterious effects of a glyphosate-based herbicide (Factor®540) on photosynthesis and related physiological processes of willow (Salix miyabeanacultivar SX64) plants. Sixty-day-old plants grown under greenhouse conditions were sprayed with different rates (0, 1.4, 2.1, and 2.8 kg a.e ha-1) of the commercial glyphosate formulated salt Factor®540. Evaluations were performed at 0, 6, 24, 48, and 72 h after herbicide exposure. We established that the herbicide decreases chlorophyll, carotenoid and plastoquinone contents, and promotes changes in the photosynthetic apparatus leading to decreased photochemistry which results in hydrogen peroxide (H2O2) accumulation. H2O2accumulation triggers proline production which can be associated with oxidative protection, NADP+recovery and shikimate pathway stimulation. Ascorbate peroxidase and glutathione peroxidase appeared to be the main peroxidases involved in the H2O2scavenging. In addition to promoting decreases of the activity of the antioxidant enzymes, the herbicide induced decreases in ascorbate pool. For the first time, a glyphosate-based herbicide mode of action interconnecting its effects on shikimate pathway, photosynthetic process and oxidative events in plants were presented.
authors.affiliation: Ecotoxicology of Aquatic Microorganisms Laboratory, GRIL, TOXEN, Department of Biological Sciences, Université du Québec à Montréal, MontréalQC, Canada; Laboratório de Fisiologia Vegetal, Instituto de Ciências Biológicas, Departamento de Botânica, Universidade Federal de Minas GeraisBelo Horizonte, Brazil.
authors.forename: Marcelo P
authors.initials: MP
authors.lastname: Gomes
authors.affiliation: Ecotoxicology of Aquatic Microorganisms Laboratory, GRIL, TOXEN, Department of Biological Sciences, Université du Québec à Montréal, Montréal QC, Canada.
authors.forename: Sarah G
authors.initials: SG
authors.lastname: Le Manac'h
authors.affiliation: Institut des Sciences de l'Environnement, Université du Québec à Montréal, Montréal QC, Canada.
authors.forename: Louise
authors.initials: L
authors.lastname: Hénault-Ethier
authors.affiliation: Institut de Recherche en Biologie Végétale, Montreal Botanical Garden, Montréal QC, Canada.
authors.forename: Michel
authors.initials: M
authors.lastname: Labrecque
authors.affiliation: Institut des Sciences de l'Environnement, Université du Québec à Montréal, Montréal QC, Canada.
authors.forename: Marc
authors.initials: M
authors.lastname: Lucotte
authors.affiliation: Ecotoxicology of Aquatic Microorganisms Laboratory, GRIL, TOXEN, Department of Biological Sciences, Université du Québec à Montréal, MontréalQC, Canada; Institut des Sciences de l'Environnement, Université du Québec à Montréal, MontréalQC, Canada.
authors.forename: Philippe
authors.initials: P
authors.lastname: Juneau
keywords: herbicide; oxidative stress; photosynthesis; proline; shikimate; willow