Response of Cucumis sativus L. seedlings to Pb exposure

Abstract

In this study, the effects of lead (Pb) on growth, photosynthetic pigments concentration, lipid peroxidation, electrolyte leakage percentage (ELP), protein oxidation, aminolevulinate dehydratase (ALA-D; E.C. 4.2.1.24), ascorbate peroxidase (APX; E.C. 1.11.1.11), catalase (CAT; E.C. 1.11.1.6) and superoxide dismutase (SOD; E.C. 1.15.1.1) activities, and ascorbic acid (AsA), nonprotein thiol groups (NPSH) and total soluble protein concentrations in cucumber seedlings (Cucumis sativus L.) were investigated. Seedlings were grown in vitro in an agar-solidified substrate containing three Pb levels as (C 2 H 3 O 2 )Pb.3H 2 O (0, 100, 400, and 1000 μmol L -1 ) for 10 d. Increasing Pb concentrations in substrate enhanced Pb concentration in both roots and shoot. Pb accumulated at a higher amount in roots. Root length and total fresh weight were decreased at the two highest Pb concentrations. Cucumber showed no reduction in shoot length and total dry weight at any Pb level. The highest Pb concentration decreased water content and ALA-D activity as well as increased malondialdehyde, carbonyls and total soluble protein concentrations. Carotenoids concentration enhanced at 100 and 400 μmol Pb L -1 , while chlorophyll concentration and ELP were not affected by Pb stress. Activity of APX was inhibited while the activities of CAT and SOD were increased at all Pb concentrations. AsA was enhanced at 400 and 1000 μmol Pb L -1 whereas NPSH were increased only at the highest Pb concentration. Therefore, high Pb-exposure caused oxidative stress, and the antioxidant system of the cucumber seedlings was not sufficient to revert it, contributing for growth reduction.

Lead tolerance and accumulation in initial sporophytes of Regnellidium diphyllum Lindm. (Marsileaceae)

“…Furthermore, this area is near a national highway with heavy traffic, which has connected the north coast of the state of Rio Grande do Sul to its capital, Porto Alegre, since it was built in 1973 (CONCEPA, 2013). Traffic on the highway may also have contributed to lead accumulation in the soil, as this metal was added to fuels between the 1970s and the 1990s, and its persistence in the environment is long (Paoliello and Chasin, 2001;Gonçalves et al, 2009).…”

“…Other sources of lead in water and soil are the mining, welding and steel production industries, effluents of domestic sewage (Gonçalves et al, 2009;García-Lestón et al, 2010), incomplete fossil fuel burning (Paoliello and Chasin, 2001), as well as agricultural inputs (Sharma and Dubey, 2005;Hu et al, 2010).…”

“…In Brazil, although this additive has been replaced with ethanol since 1993, significant levels of lead are still present in ecosystems due to the persistence of this metal in the environment (Paoliello and Chasin, 2001;Gonçalves et al, 2009).…”

“…The excess of lead can cause toxicity symptoms such as growth reduction, chlorosis, inhibition of photosynthesis, and changes in mineral nutrition and in the availability of growth factors. Plants that survive in lead contaminated soil may present morphological, physiological and biochemical alterations, and may develop mechanisms for detoxification and tolerance, such as accumulating lead in the vacuoles and cell walls of roots and aerial parts (Sharma and Dubey, 2005;Mishra and Tripathi, 2008;Gonçalves et al, 2009).…”

The Different Physiological and Antioxidative Responses of Zucchini and Cucumber to Sewage Sludge Application

“…Many worldwide studies report that abiotic stresses, such as the presence in soil of inorganic compounds, such as heavy metals [ 35 ], or organic compounds, such as PCBs and PCDD/F [ 5 ], or the presence of osmotic stress [ 36 ], UV radiation [ 37 ] and acid rain [ 38 – 40 ] are the main causes of secondary oxidative stress [ 41 ]. This phenomenon, occurring in plant tissues, is characterized with overproduction of Reactive Oxygen Species (ROS) such as superoxide anions (O 2 -· ), hydroxyl radicals (·OH) and peroxyl radicals (ROO·), singlet oxygen ( 1 O 2 ) and hydrogen peroxide (H 2 O 2 ).…”