title: Lettuce irrigated with contaminated water: Photosynthetic effects, antioxidative response and bioaccumulation of microcystin congeners.
abstract: The use of microcystins (MCs) contaminated water to irrigate crop plants represents a human health risk due to their bioaccumulation potential. In addition, MCs cause oxidative stress and negatively influence photosynthetic activities in plants. The present study was aimed at investigating the effect of MCs on photosynthetic parameters and antioxidative response of lettuce. Furthermore, the bioaccumulation factor (BAF) of total MCs, MC-LR and MC-RR in the vegetable after irrigation with contaminated water was determined. Lettuce crops were irrigated for 15 days with water containing cyanobacterial crude extracts (Microcystis aeruginosa) with MC-LR (0.0, 0.5, 2.0, 5.0 and 10.0 µg L(-1)), MC-RR (0.0, 0.15, 0.5, 1.5 and 3.0 µg L(-1)) and total MCs (0.0, 0.65, 2.5, 6.5 and 13.0 µg L(-1)). Increased net photosynthetic rate, stomatal conductance, leaf tissue transpiration and intercellular CO2 concentration were recorded in lettuce exposed to different MCs concentrations. Antioxidant response showed that glutathione S-transferase activity was down-regulated in the presence of MCs. On the other hand, superoxide dismutase, catalase and peroxidase activities were upregulated with increasing MCs concentrations. The bioaccumulation factor (BAF) of total MCs and MC-LR was highest at 6.50 and 5.00 µg L(-1), respectively, while for MC-RR, the highest BAF was recorded at 1.50 µg L(-1) concentration. The amount of total MCs, MC-LR and MC-RR bioacumulated in lettuce was highest at the highest exposure concentrations. However, at the lowest exposure concentration, there were no detectable levels of MC-LR, MC-RR and total MCs in lettuce. Thus, the bioaccumulation of MCs in lettuce varies according to the exposure concentration. In addition, the extent of physiological response of lettuce to the toxins relies on exposure concentrations.
authors.affiliation: Departamento de Ciências Biológicas, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Av. Pádua Dias, 11, São Dimas, Piracicaba, CEP 13418-900 SP, Brazil; Programa de Pós-Graduação em Botânica, Universidade Federal Rural de Pernambuco, R. Dom Manoel de Medeiros, s/n, Dois Irmãos, Recife, CEP 52171-030 PE, Brazil. Electronic address: mbitt@usp.br.
authors.forename: Maria do Carmo
authors.initials: Mdo C
authors.lastname: Bittencourt-Oliveira
authors.affiliation: Departamento de Ciências Biológicas, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Av. Pádua Dias, 11, São Dimas, Piracicaba, CEP 13418-900 SP, Brazil; Programa de Pós-Graduação em Botânica, Universidade Federal Rural de Pernambuco, R. Dom Manoel de Medeiros, s/n, Dois Irmãos, Recife, CEP 52171-030 PE, Brazil.
authors.forename: Micheline Kézia
authors.initials: MK
authors.lastname: Cordeiro-Araújo
authors.affiliation: Departamento de Ciências Biológicas, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Av. Pádua Dias, 11, São Dimas, Piracicaba, CEP 13418-900 SP, Brazil.
authors.forename: Mathias Ahii
authors.initials: MA
authors.lastname: Chia
authors.affiliation: Instituto de Física, Universidade de São Paulo, Rua do Matão Travessa R Nr.187, Cidade Universitária, CEP 05508-090 SP, Brazil; FESP - São Paulo Engineering College, Av. 9 de Julho, 5520 - Jardim Europa, São Paulo, CEP 01406-200 SP, Brazil.
authors.forename: João Dias de Toledo
authors.initials: JD
authors.lastname: Arruda-Neto
authors.affiliation: Departamento de Ciências Biológicas, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Av. Pádua Dias, 11, São Dimas, Piracicaba, CEP 13418-900 SP, Brazil.
authors.forename: Ênio Tiago
authors.initials: ÊT
authors.lastname: de Oliveira
authors.affiliation: Departamento de Ciências Biológicas, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Av. Pádua Dias, 11, São Dimas, Piracicaba, CEP 13418-900 SP, Brazil.
authors.forename: Flávio
authors.initials: F
authors.lastname: dos Santos
mesh_terms: D057914:Agricultural Irrigation; D000975:Antioxidants / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D018545:Lactuca / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D052998:Microcystins / Q000378:metabolism* / Q000633:toxicity; D046931:Microcystis / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D010788:Photosynthesis / Q000187:drug effects*; D018515:Plant Leaves / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000378:metabolism* / Q000633:toxicity
chemical_list: D000975:Antioxidants; D052998:Microcystins; D014874:Water Pollutants, Chemical; D002374:Catalase; D005982:Glutathione Transferase
keywords: Food contamination; Human health; Microcystins; Oxidative stress; Photosynthesis