title: Physiological mechanisms to cope with Cr(VI) toxicity in lettuce: can lettuce be used in Cr phytoremediation?
abstract: This research aims at identifying the main deleterious effects of Cr(VI) on the photosynthetic apparatus and at selecting the most sensitive endpoints related to photosynthesis. To achieve this goal, we used lettuce (Lactuca sativa), a sensible ecotoxicological crop model. Three-week-old plants were exposed to 0, 50, 150 and 200 mg L(-1) of Cr(VI). These concentrations ranged from levels admitted in irrigation waters to values found in several Cr industry effluents and heavily contaminated environments. After 30 days of exposure, plants accumulated Cr preferably in roots and showed nutritional impairment, with decreases of K, Mg, Fe and Zn in both roots and leaves. Cr(VI)-exposed plants showed decreased levels of chlorophyll (Chl) a and anthocyanins, as well as decreased effective quantum yield of photostystem II (ΦPSII) and photochemical Chl fluorescence quenching (qp), but increases in the non-photochemical Chl fluorescence quenching (NPQ) and in the de-epoxidation state (DEP) of the xanthophyll cycle. Net CO2 assimilation rate (P N ) and RuBisCO activity were mostly impaired in the highest Cr(VI) concentration tested. Concerning the final products of photosynthesis, starch content was not affected, while soluble sugar contents increased. These alterations were accompanied by a reduction in protein content and in plant growth. Our results support that endpoints related to the photosynthesis photochemical processes (ΦPSII and the qp) and the content of anthocyanins are sensitive predictors of Cr(VI) toxicity. The advantages of using these parameters as biomarkers for Cr toxicity in plants are discussed. Finally, we report that, despite showing physiological disorders, L. sativa plants survived and accumulated high doses of Cr, and their use in environmental/decontamination studies is open to debate.
authors.affiliation: Centre for Functional Ecology (CEF) and Department of Life Science, University of Coimbra, Calçada Martim de Freitas, 3000-456, Coimbra, Portugal. celeste.dias@uc.pt.|Department of Chemistry and QOPNA, University of Aveiro, 3810-193, Aveiro, Portugal. celeste.dias@uc.pt.
authors.forename: Maria Celeste
authors.initials: MC
authors.lastname: Dias
authors.affiliation: Department of Biology and Environment, Centre for the Research and Technology of Agro-Environmental and Biological Sciences (CITAB), University of Trás-os-Montes e Alto Douro, Apartado 1013, 5001-801, Vila Real, Portugal.
authors.forename: José
authors.initials: J
authors.lastname: Moutinho-Pereira
authors.affiliation: Department of Biology and Environment, Centre for the Research and Technology of Agro-Environmental and Biological Sciences (CITAB), University of Trás-os-Montes e Alto Douro, Apartado 1013, 5001-801, Vila Real, Portugal.
authors.forename: Carlos
authors.initials: C
authors.lastname: Correia
authors.affiliation: Laboratory of Biotechnology and Cytometry, University Aveiro, 3810-193, Aveiro, Portugal.
authors.forename: Cristina
authors.initials: C
authors.lastname: Monteiro
authors.affiliation: Laboratory of Biotechnology and Cytometry, University Aveiro, 3810-193, Aveiro, Portugal.
authors.forename: Márcia
authors.initials: M
authors.lastname: Araújo
authors.affiliation: Department of Ecology, Evolution and Diversity, Goethe University, Max von Laue Str. 13, 60438, Frankfurt am Main, Germany.|Biodiversity and Climate Research Centre, Senckenberganlage 25, 60325, Frankfurt am Main, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Brüggemann
authors.affiliation: Department of Biology & GreenUP/Citab-UP, Faculty of Sciences, University of Porto, Rua do Campo Alegre, 4169-007, Porto, Portugal.
authors.forename: Conceição
authors.initials: C
authors.lastname: Santos
mesh_terms: D001673:Biodegradation, Environmental; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D002857:Chromium / Q000378:metabolism / Q000494:pharmacology*; D018545:Lactuca / Q000187:drug effects* / Q000378:metabolism; D010788:Photosynthesis / Q000187:drug effects; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism
chemical_list: D002857:Chromium; D002734:Chlorophyll; C074702:chromium hexavalent ion; D000077194:Chlorophyll A
keywords: Chlorophyll fluorescence; Photosynthesis; Pigments; Proline; RuBisCO