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Ecophysiological tolerance of duckweeds exposed to copper.
Aquat Toxicol. 2009 Jan 18; 91(1):1-9.AT

Abstract

Although essential for plants, copper can be toxic when present in supra-optimal concentrations. Metal polluted sites, due to their extreme conditions, can harbour tolerant species and/or ecotypes. In this work we aimed to compare the physiological responses to copper exposure and the uptake capacities of two species of duckweed, Lemna minor (Lm(EC1)) and Spirodela polyrrhiza (SP), from an abandoned uranium mine with an ecotype of L. minor (Lm(EC2)) from a non-contaminated pond. From the lowest Cu concentration exposure (25microM) to the highest (100microM), Lm(EC2) accumulated higher amounts of copper than Lm(EC1) and SP. Dose-response curves showed that Cu content accumulated by Lm(EC2) increases linearly with Cu treatment concentrations (r(2)=0.998) whereas quadratic models were more suitable for Lm(EC1) and SP (r(2)=0.999 and r(2)=0.998 for Lm(EC1) and SP, respectively). A significant concentration-dependent decline of chlorophyll a (chl a) and carotenoid occurred as a consequence of Cu exposure. These declines were significant for Lm(EC2) exposed to the lowest Cu concentration (25microM) whereas for Lm(EC1) and SP a significant decrease in chl a and carotenoids was observed only at 50 and 100microM-Cu. Electric conductivity (EC) and malondialdehyde (MDA) content increased after Cu exposure, indicating oxidative stress. Significant increase of EC was observed in Lm(EC2) for all Cu concentrations whereas the increase for Lm(EC1) and SP became significant only after an exposure to 50microM-Cu. On the contrary, for Lm(EC1), SP, and Lm(EC2), MDA content significantly increased even at the lowest concentration. Protein content and catalase (CAT) activity showed a decrease with an increase in Cu concentration. For the species Lm(EC1) and SP, a significant effect of copper on CAT activity was observed only at the highest concentration (100microM-Cu) whereas, for Lm(EC2), this effect started to be significant after an exposure to 50microM-Cu. Superoxide dismutase (SOD) activity increased with increasing concentrations of Cu, with a very similar trend between the three populations of duckweed. However, due to the facts that enzyme activity is expressed as units of activity per gram of protein and that protein content decreased with Cu exposure, the increase in SOD activity might partly result from a relative increase of this enzyme inside the pool of proteins. Consequently, the results obtained in our experimental conditions strongly suggest that duckweed species from the uranium-polluted area have developed mechanisms to cope with metal toxicity and that this tolerance is based on the existence of protective mechanism to limit the metal uptake rather than on an enhancement of the antioxidative metabolism.

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Publisher Full Text (DOI)

Authors+Show Affiliations

Kanoun-Boulé M
Centre for Functional Ecology, Department of Botany, University of Coimbra, Coimbra 3000-456, Portugal. mkb@ci.uc.pt
Vicente JA
No affiliation info available
Nabais C
No affiliation info available
Prasad MN
No affiliation info available
Freitas H
No affiliation info available

MeSH

AraceaeCarotenoidsCatalaseChlorophyllCopperElectrolytesFresh WaterLipid PeroxidationProteinsSuperoxide DismutaseWater Pollutants, Chemical

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

19027182

Citation

Kanoun-Boulé, Myriam, et al. "Ecophysiological Tolerance of Duckweeds Exposed to Copper." Aquatic Toxicology (Amsterdam, Netherlands), vol. 91, no. 1, 2009, pp. 1-9.
Kanoun-Boulé M, Vicente JA, Nabais C, et al. Ecophysiological tolerance of duckweeds exposed to copper. Aquat Toxicol. 2009;91(1):1-9.
Kanoun-Boulé, M., Vicente, J. A., Nabais, C., Prasad, M. N., & Freitas, H. (2009). Ecophysiological tolerance of duckweeds exposed to copper. Aquatic Toxicology (Amsterdam, Netherlands), 91(1), 1-9. https://doi.org/10.1016/j.aquatox.2008.09.009
Kanoun-Boulé M, et al. Ecophysiological Tolerance of Duckweeds Exposed to Copper. Aquat Toxicol. 2009 Jan 18;91(1):1-9. PubMed PMID: 19027182.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Ecophysiological tolerance of duckweeds exposed to copper. AU - Kanoun-Boulé,Myriam, AU - Vicente,Joaquim A F, AU - Nabais,Cristina, AU - Prasad,M N V, AU - Freitas,Helena, Y1 - 2008/09/21/ PY - 2008/02/04/received PY - 2008/09/10/revised PY - 2008/09/13/accepted PY - 2008/11/26/entrez PY - 2008/11/26/pubmed PY - 2009/1/22/medline SP - 1 EP - 9 JF - Aquatic toxicology (Amsterdam, Netherlands) JO - Aquat Toxicol VL - 91 IS - 1 N2 - Although essential for plants, copper can be toxic when present in supra-optimal concentrations. Metal polluted sites, due to their extreme conditions, can harbour tolerant species and/or ecotypes. In this work we aimed to compare the physiological responses to copper exposure and the uptake capacities of two species of duckweed, Lemna minor (Lm(EC1)) and Spirodela polyrrhiza (SP), from an abandoned uranium mine with an ecotype of L. minor (Lm(EC2)) from a non-contaminated pond. From the lowest Cu concentration exposure (25microM) to the highest (100microM), Lm(EC2) accumulated higher amounts of copper than Lm(EC1) and SP. Dose-response curves showed that Cu content accumulated by Lm(EC2) increases linearly with Cu treatment concentrations (r(2)=0.998) whereas quadratic models were more suitable for Lm(EC1) and SP (r(2)=0.999 and r(2)=0.998 for Lm(EC1) and SP, respectively). A significant concentration-dependent decline of chlorophyll a (chl a) and carotenoid occurred as a consequence of Cu exposure. These declines were significant for Lm(EC2) exposed to the lowest Cu concentration (25microM) whereas for Lm(EC1) and SP a significant decrease in chl a and carotenoids was observed only at 50 and 100microM-Cu. Electric conductivity (EC) and malondialdehyde (MDA) content increased after Cu exposure, indicating oxidative stress. Significant increase of EC was observed in Lm(EC2) for all Cu concentrations whereas the increase for Lm(EC1) and SP became significant only after an exposure to 50microM-Cu. On the contrary, for Lm(EC1), SP, and Lm(EC2), MDA content significantly increased even at the lowest concentration. Protein content and catalase (CAT) activity showed a decrease with an increase in Cu concentration. For the species Lm(EC1) and SP, a significant effect of copper on CAT activity was observed only at the highest concentration (100microM-Cu) whereas, for Lm(EC2), this effect started to be significant after an exposure to 50microM-Cu. Superoxide dismutase (SOD) activity increased with increasing concentrations of Cu, with a very similar trend between the three populations of duckweed. However, due to the facts that enzyme activity is expressed as units of activity per gram of protein and that protein content decreased with Cu exposure, the increase in SOD activity might partly result from a relative increase of this enzyme inside the pool of proteins. Consequently, the results obtained in our experimental conditions strongly suggest that duckweed species from the uranium-polluted area have developed mechanisms to cope with metal toxicity and that this tolerance is based on the existence of protective mechanism to limit the metal uptake rather than on an enhancement of the antioxidative metabolism. SN - 1879-1514 UR - https://www.unboundmedicine.com/medline/citation/19027182/Ecophysiological_tolerance_of_duckweeds_exposed_to_copper_ DB - PRIME DP - Unbound Medicine ER -