title: Leaf Age-Dependent Photoprotective and Antioxidative Response Mechanisms to Paraquat-Induced Oxidative Stress in Arabidopsis thaliana.
abstract: Exposure of Arabidopsis thaliana young and mature leaves to the herbicide paraquat (Pq) resulted in a localized increase of hydrogen peroxide (H2O2) in the leaf veins and the neighboring mesophyll cells, but this increase was not similar in the two leaf types. Increased H2O2 production was concomitant with closed reaction centers (qP). Thirty min after Pq exposure despite the induction of the photoprotective mechanism of non-photochemical quenching (NPQ) in mature leaves, H2O2 production was lower in young leaves mainly due to the higher increase activity of ascorbate peroxidase (APX). Later, 60 min after Pq exposure, the total antioxidant capacity of young leaves was not sufficient to scavenge the excess reactive oxygen species (ROS) that were formed, and thus, a higher H2O2 accumulation in young leaves occurred. The energy allocation of absorbed light in photosystem II (PSII) suggests the existence of a differential photoprotective regulatory mechanism in the two leaf types to the time-course Pq exposure accompanied by differential antioxidant protection mechanisms. It is concluded that tolerance to Pq-induced oxidative stress is related to the redox state of quinone A (QA).
authors.affiliation: Department of Botany, School of Biology, Aristotle University of Thessaloniki, University Campus, 54124 Thessaloniki, Greece. grad738@edu.biology.uoc.gr.
authors.forename: Julietta
authors.initials: J
authors.lastname: Moustaka
authors.affiliation: Faculty of Agriculture, Forestry and Natural Environment, School of Agriculture, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece. gtanou@agro.auth.gr.
authors.forename: Georgia
authors.initials: G
authors.lastname: Tanou
authors.affiliation: Department of Botany, School of Biology, Aristotle University of Thessaloniki, University Campus, 54124 Thessaloniki, Greece. iadamaki@bio.auth.gr.
authors.forename: Ioannis-Dimosthenis
authors.initials: ID
authors.lastname: Adamakis
authors.affiliation: Department of Botany, School of Biology, Aristotle University of Thessaloniki, University Campus, 54124 Thessaloniki, Greece. eelefth@bio.auth.gr.
authors.forename: Eleftherios P
authors.initials: EP
authors.lastname: Eleftheriou
authors.affiliation: Department of Botany, School of Biology, Aristotle University of Thessaloniki, University Campus, 54124 Thessaloniki, Greece. moustak@bio.auth.gr.
authors.forename: Michael
authors.initials: M
authors.lastname: Moustakas
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D017360:Arabidopsis / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects*; D006861:Hydrogen Peroxide / Q000378:metabolism; D008027:Light; D016877:Oxidants / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D010269:Paraquat / Q000494:pharmacology*; D010575:Pesticides / Q000494:pharmacology*; D018515:Plant Leaves / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects
chemical_list: D000975:Antioxidants; D016877:Oxidants; D010575:Pesticides; D006861:Hydrogen Peroxide; D010269:Paraquat
keywords: antioxidant enzymes; chlorophyll fluorescence; differential response; electron transport; herbicides; hydrogen peroxide; non-photochemical quenching; reactive oxygen species