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M Cu (m + cu)
Selected AbstractsPhysiological responses of Matricaria chamomilla to cadmium and copper excessENVIRONMENTAL TOXICOLOGY, Issue 1 2008Jozef Ková Abstract Physiological responses of Matricaria chamomilla plants exposed to cadmium (Cd) and copper (Cu) excess (3, 60, and 120 ,M for 7 days) with special emphasis on phenolic metabolism were studied. Cu at 120 ,M reduced chamomile growth, especially in the roots where it was more abundant than Cd. Notwithstanding the low leaf Cu amount (37.5 ,g g,1 DW) in comparison with Cd (237.8 ,g g,1 DW) at 120 ,M, it caused reduction of biomass accumulation, Fv/Fm ratio and soluble proteins. In combination with high accumulation of phenolics, strong reduction of proteins and high GPX activity in the roots, this supports severe redox Cu properties. In terms of leaf phenylalanine ammonia-lyase (PAL) activity, it seems that Cd had a stimulatory effect during the course of the experiment, whereas Cu was found to stimulate it after 7-day exposure. The opposite trend was visible in the roots, where Cd had a stimulatory effect at high doses but Cu mainly at the highest dose. This supports the assumption of different PAL time dynamics under Cd and Cu excess. A dose of 60 and 120 ,M Cu led to 2- and 3-times higher root lignin accumulation while the same Cd doses increased it by 33 and 68%, respectively. A Cu dose of 120 ,M can be considered as limiting for chamomile growth under conditions of present research, while resistance to high Cd doses was confirmed. However, PAL and phenolics seemed to play an important role in detoxification of Cd- and Cu-induced oxidative stress. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008. [source] Copper toxicity in relation to surface water-dissolved organic matter: Biological effects to Daphnia magnaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2004Kees J.M. Kramer Abstract Water quality standards for copper are usually stated in total element concentrations. It is known, however, that a major part of the copper can be bound in complexes that are biologically not available. Natural organic matter, such as humic and fulvic acids, are strong complexing agents that may affect the bioavailable copper (Cu2+) concentration. The aim of this study was to quantify the relation between the concentration of dissolved natural organic matter and free Cu2+ in surface waters, and the biological effect, as measured in a standardized ecotoxicological test (48 h-median effective concentration [EC50] Daphnia magna, mobility). Six typical Dutch surface waters and an artificial water, ranging from 0.1 to 22 mg/L dissolved organic carbon (DOC), were collected and analyzed quarterly. Chemical speciation modeling was used as supporting evidence to assess bioavailability. The results show clear evidence of a linear relation between the concentration of dissolved organic carbon (in milligrams DOC/L) and the ecotoxicological effect (as effect concentration, EC50, expressed as micrograms Cu/L): 48-h EC50 (Daphnia, mobility) = 17.2 × DOC + 30.2 (r2 = 0.80, n = 22). Except for a brook with atypical water quality characteristics, no differences were observed among water type or season. When ultraviolet (UV)-absorption (380 nm) was used to characterize the dissolved organic carbon, a linear correlation was found as well. The importance of the free copper concentration was demonstrated by speciation calculations: In humic-rich waters the free Cu2+ concentration was estimated at ,10,11 M, whereas in medium to low dissolved organic carbon waters the [Cu2+] was ,10,10 M. Speciation calculations performed for copper concentrations at the effective concentration level (where the biological effect is considered the same) resulted in very similar free copper concentrations (,10,8 M Cu) in these surface waters with different characteristics. These observations consistently show that the presence of organic matter decreases the bioavailability, uptake, and ecotoxicity of copper in the aquatic environment. It demonstrates that the DOC content must be included in site-specific environmental risk assessment for trace metals (at least for copper). It is the quantification of the effects described that allows policy makers to review the criteria for copper in surface waters. [source] Development of photosynthetic biofilms affected by dissolved and sorbed copper in a eutrophic riverENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2002Christiane Barranguet Abstract Photosynthetic biofilms are capable of immobilizing important concentrations of metals, therefore reducing bioavailability to organisms. But also metal pollution is believed to produce changes in the microalgal species composition of biofilms. We investigated the changes undergone by natural photosynthetic biofilms from the River Meuse, The Netherlands, under chronic copper (Cu) exposure. The suspended particles in the river water had only a minor effect on reduction of sorption and toxicity of Cu to algae. Biofilms accumulated Cu proportionally to the added concentration, also at the highest concentration used (9 ,M Cu). The physiognomy of the biofilms was affected through the growth of the chain-forming diatom Melosira varians, changing from long filaments to short tufts, although species composition was not affected by the Cu exposure. The Cu decreased phosphate uptake and algal biomass measured as chl a, which degraded exponentially in time. Photosynthetic activity was always less sensitive than algal biomass; the photon yield decreased linearly in time. The protective and insulating role of the biofilm, supported by ongoing autotrophic activity, was indicated as essential in resisting metal toxicity. We discuss the hypothesis that the toxic effects of Cu progress almost independently of the species composition, counteracting ongoing growth, and conclude that autotrophic biofilms act as vertical heterogeneous units. Effective feedback mechanisms and density dependence explain several discrepancies observed earlier. [source] In vitro selection and plant regeneration of copper-tolerant plants from leaf explants of Nicotiana tabacum L. cv. ,Xanthi'PLANT BREEDING, Issue 4 2007G. R. Rout Abstract Copper tolerance of Nicotiana tabacum L. var. Xanthi in vitro was achieved through plant regeneration from leaf explants on Murashige and Skoog's (MS) medium supplemented with 0.5 mg/l BA, 0.1,0.25 mg/l IAA and 60 ,m Cu. Tolerant organogenic calli showed more vigorous growth in medium containing 60 ,m Cu than the non-tolerant calli. Standard growth parameters such as fresh and dry weight of organogenic callus, growth tolerance index (GTI), enzyme activity (peroxidase and catalase) and copper accumulation were used as indicators of copper tolerance. The activities of peroxidase and catalase as well as estimation of protein, total amino acid and chlorophyll were greater in tolerant calli than non-tolerant ones. The GTI in the 4 weeks after the beginning of treatments yielded significant differences among the tolerant and non-tolerant organogenic callus cultures. The accumulation of copper in the tolerant calli increased significantly with an increase in copper concentration in the medium. Shoot bud regeneration was achieved in both tolerant and non-tolerant organogenic calli on MS medium containing 0.5 mg/l BA and 0.1 mg/l IAA. The tolerant regenerated shoots were rooted on half-strength basal MS medium with 60 ,m Cu for selection of tolerant clones. This study may help in the selection and characterization of Cu-tolerant lines of N. tabacum cv. ,Xanthi' for building conservation strategies and also for phytoremediation programmes. [source] | ||||||||||